What is the Value of X Given That Pq Bc

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Mathematics Part II Solutions Solutions for Class 10 Math Chapter 1 Similarity are provided here with simple step-by-step explanations. These solutions for Similarity are extremely popular among Class 10 students for Math Similarity Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Mathematics Part II Solutions Book of Class 10 Math Chapter 1 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Mathematics Part II Solutions Solutions. All Mathematics Part II Solutions Solutions for class Class 10 Math are prepared by experts and are 100% accurate.

Question 1:

Base of a triangle is 9 and height is 5. Base of another triangle is 10 and height is 6. Find the ratio of areas of these triangles.

Let ABC and PQR be two right triangles with AB ⊥ BC and PQ ⊥ QR.
Given:
BC = 9, AB = 5, PQ = 6 and QR = 10.

$\therefore$

A

ABC

A

PQR

=

AB
×
BC

PQ
×
QR

=

5
×
9

6
×
10

=

3
4

Question 2:

In the given figure, BC ⊥ AB, AD ⊥ AB, BC = 4, AD = 8, then find

$\frac{}{}$

A

ABC

A

.

Given:
BC = 4

$\therefore$

A

ABC

A

=

AB
×
BC

AB
×

=

BC

BC
=
4

and

=
8

=

4
8

$=$

1
2

Question 3:

In adjoining figure, seg PS ⊥ seg RQ seg QT ⊥ seg PR. If RQ = 6, PS = 6 and PR = 12, then Find QT.

Given:
PS ⊥ RQ
QT ⊥ PR
RQ = 6, PS = 6 and PR = 12
With base PR and height QT,

$\mathrm{A}$

PQR

=

1
2

×
PR
×
QT

With base QR and height PS,

$\mathrm{A}$

PQR

=

1
2

×
QR
×
PS

$\therefore$

A

PQR

A

PQR

=

1
2

×
PR
×
QT

1
2

×
QR
×
PS

1
=

PR
×
QT

QR
×
PS

PR
×
QT
=
QR
×
PS

$⇒$
QT
=

QR
×
PS

PR

=

6
×
6

12

=
3

Hence, the measure of side QT is 3 units.

Question 4:

In adjoining figure, AP ⊥ BC, AD || BC, then Find A(∆ABC) : A(∆BCD).

Given:
AP ⊥ BC

$\therefore$

A

ABC

A

BCD

=

AP
×
BC

AP
×
BC

=

1
1

Hence, the ratio of A(∆ABC) and A(∆BCD) is 1 : 1.

Question 5:

In adjoining figure PQ ⊥ BC, AD⊥ BC then find following ratios.

(i)

$\frac{}{}$

A

PQB

A

PBC

(ii)

$\frac{}{}$

A

PBC

A

ABC

(iii)

$\frac{}{}$

A

ABC

A

(iv)

$\frac{}{}$

A

A

PQC

(i)

$\frac{}{}$

A

PQB

A

PBC

=

PQ
×
BQ

PQ
×
BC

=

BQ
BC

(ii)

$\frac{}{}$

A

PBC

A

ABC

=

PQ
×
BC

×
BC

=

PQ

(iii)

$\frac{}{}$

A

ABC

A

=

×
BC

×
DC

=

BC
DC

(iv)

$\frac{}{}$

A

A

PQC

=

×
DC

PQ
×
QC

Question 1:

Given below are some triangles and lengths of line segments. Identify in which figures, ray PM is the bisector of ∠QPR.
(1)

(2)

(3)

(1)

$\mathrm{In}$

QMP
,

QM
QP

=

3
.
5

7

=

1
2

$\mathrm{In}$

MRP
,

MR
RP

=

1
.
5

3

=

1
2

$\therefore$

QM
QP

=

MR
RP

By converse of angle bisector theorem, ray PM is the bisector of ∠QPR.

(2)

$\mathrm{In}$

QMP
,

QM
QP

=

8
10

=

4
5

$\mathrm{In}$

MRP
,

MR
RP

=

6
7

$\therefore$

QM
QP

MR
RP

Therefore, ray PM is not the the bisector of ∠QPR.
(3)

$\mathrm{In}$

QMP
,

QM
QP

=

3
.
6

9

=

2
5

$\mathrm{In}$

MRP
,

MR
RP

=

4
10

=

2
5

$\therefore$

QM
QP

=

MR
RP

By converse of angle bisector theorem, ray PM is the bisector of ∠QPR.

Question 2:

In ∆PQR, PM = 15, PQ = 25 PR = 20, NR = 8. State whether line NM is parallel to side RQ. Give reason.

Given:
PM = 15,
PQ = 25,
PR = 20 and
NR = 8
Now, PN = PR − NR
= 20 − 8
= 12
Also, MQ = PQ − PM
= 25 − 15
= 10

$\mathrm{In}$

PRQ
,

PR
NR

=

12
8

=

3
2

$\mathrm{Also}$
,

PM
MQ

=

15
10

=

3
2

$\therefore$

PR
NR

=

PM
MQ

By converse of basic proportionality theorem, NM is parallel to side RQ or NM || RQ.

Question 3:

In ∆MNP, NQ is a bisector of ∠N. If MN = 5, PN = 7 MQ = 2.5 then Find QP.

$\mathrm{In}$

PNM
,

QM
QP

=

MN
PN

By

angle

bisector

theorem

2
.
5

QP

=

5
7

$⇒$
QP
=

2
.
5
×
7

5

=
3
.
5

Hence, the measure of QP is 3.5.

Question 4:

Measures of some angles in the figure are given. Prove that

$\frac{}{}$
AP
PB

=

AQ
QC

Given:
∠APQ = 60

∠ABC = 60

Since, the corresponding angles ∠APQ and ​∠APC are equal.
Hence, line PQ || BC.

$\mathrm{In}$

ABC
,

PQ

B
C

AP
PB

=

AQ
QC

By

Basic

proportionality
theorem

Question 5:

In trapezium ABCD, side AB || side PQ || side ∆C, AP = 15, PD = 12, QC = 14, Find BQ.

Construction: Join BD intersecting PQ at X.

In △ABD, PX || AB

$\frac{}{}$
DP
PA

=

DX
XB

.
.
.

1

By

Basic

proportionality

theorem

In △BDC, XQ||DC

$\frac{}{}$
DX
XB

=

CQ
QB

.
.
.

2

By

Basic

proportionality

theorem

From (1) and (2), we get

$\frac{}{}$
DP
PA

=

CQ
QB

12
15

=

14
QB

QB
=
17
.
5

Question 6:

Find QP using given information in the figure.

$\mathrm{In}$

PNM
,

QM
QP

=

MN
PN

By

angle

bisector

theorem

14
QP

=

25
40

$⇒$
QP
=

14
×
40

25

=
22
.
4

Hence, the measure of QP is 22.4.

Question 7:

In the given figure, if AB || CD || FE then Find
x
and AE.

Construction: Join AFintersecting CD at X.

In △ABF, DX || AB

$\frac{}{}$
FD
DB

=

FX
XA

.
.
.

1

By

Basic

proportionality

theorem

In △AEF, XC||FE

$\frac{}{}$
FX
XA

=

EC
CA

.
.
.

2

By

Basic

proportionality

theorem

From (1) and (2), we get

$\frac{}{}$
FD
DB

=

EC
CA

4
8

=

x
12

x
=
6

Now, AE = AC + CE
= 12 + 6
= 18

Question 8:

In ∆LMN, ray MT bisects ∠LMN If LM = 6, MN = 10, TN = 8, then Find LT.

$\mathrm{In}$

LNM
,

LT
NT

=

LM
NM

By

angle

bisector

theorem

LT
8

=

6
10

$⇒$
LT
=

8
×
6

10

=
4
.
8

Hence, the measure of LT is 4.8.

Page No 15:

In △ABC, ∠ABD = ∠DBC

$\frac{}{}$
DC

=

AB
CB

By

angle

bisector

theorem

x

2

x
+
2

=

x

x
+
5

x
2

+
3
x

10
=

x
2

+
2
x

$⇒$
3
x

2
x
=
10

x
=
10

Question 10:

In the given figure, X is any point in the interior of triangle. Point X is joined to vertices of triangle. Seg PQ || seg DE, seg QR || seg EF. Fill in the blanks to prove that, seg PR || seg DF.

Given:
Seg PQ || seg DE
seg QR || seg EF
In △DXE, PQ || DE

$\frac{}{}$
XP

PD

=

XQ

QE

.
.
.

I

By

basic

proportionality

theorem

In △XEF, QR || EF                ….Given

$\therefore$

XQ

QE

=

XR

RF

.
.
.
.
.

II

By

basic

proportionality

theorem

$\therefore$

XP

PD

=

XR

RF

From

I

and

II

∴ seg PR || seg DF        (Converse of basic proportional theorem)

Question 11:

In ∆ABC, ray BD bisects ∠ABC and ray CE bisects ∠ACB. If seg AB ≅ seg AC then prove that ED || BC.

Given:
ray BD bisects ∠ABC
ray CE bisects ∠ACB.
seg AB ≅ seg AC

In △ABC, ∠ABD = ∠DBC

$\frac{}{}$
DC

=

AB
BC

.
.
.

I

By

angle

bisector

theorem

In △ABC, ∠BCE = ∠ACE

$\frac{}{}$
AE
EB

=

AC
BC

.
.
.

II

By

angle

bisector

theorem

From (I) and (II)

$\frac{}{}$
DC

=

AE
EB

seg

AB

seg

AC

∴ ​ED || BC        (Converse of basic proportional theorem)

Question 1:

In the given figure, ∠ABC = 75°, ∠EDC = 75° state which two triangles are similar and by which test? Also write the similarity of these two triangles by a proper one to one correspondence.

Given:
∠ABC = 75°, ∠EDC = 75°
Now, in △ABC and △EDC
∠ABC = ∠EDC = 75°         (Given)
∠C = ∠C         (Common)
By AA test of similarity
△ABC ∼ △EDC

Question 2:

Are the triangles in the given figure similar? If yes, by which test ?

Given:
PQ = 6
PR = 10
QR = 8
LM = 3
LN = 5
MN = 4
Now,

$\frac{}{}$
PQ
LM

=

6
3

=
2
,

QR

MN

=

8

4

=
2
,

RP

NL

=

10

5

=
2

$\therefore$

PQ
LM

=

QR

MN

=

RP

NL

By SSS test of similarity
△PQR ∼ △LMN

Question 3:

As shown in the given figure, two poles of height 8 m and 4 m are perpendicular to the ground. If the length of shadow of smaller pole due to sunlight is 6 m then how long will be the shadow of the bigger pole at the same time ?

Given:
PR = 4
RL = 6
AC = 8
In △PLR and △ABC
∠PRL = ∠ACB         (Vertically opposite angles)
∠LPR = ∠BAC         (Angles made by sunlight on top are congruent)
By AA test of similarity
△PLR ∼ △ABC

$\therefore$

PR
AC

=

LR

BC

Corresponding

sides

are

proportional

4
8

=

6
x

x
=
12

Hence, the length of shadow of bigger pole due to sunlight is 12 m.

Question 4:

In ∆ABC, AP ⊥ BC, BQ ⊥ AC B– P–C, A–Q – C then prove that, ∆CPA ~ ∆CQB. If AP = 7, BQ = 8, BC = 12 then Find AC.

Given:
AP ⊥ BC
BQ ⊥ AC
To prove: ∆CPA ~ ∆CQB
Proof: In ∆CPA and ∆CQB
∠CPA = ∠CQB = 90         (Given)
∠C = ∠C                             (Common)
By AA test of similarity
∆CPA ~ ∆CQB
Hence proved.

$\mathrm{Now}$
,

AP
BQ

=

AC

BC

Corresponding

sides

are

proportional

AC
=

AP
BQ

×
BC

=

7
8

×
12

=
10
.
5

Question 5:

Given :
In trapezium PQRS, side PQ || side SR, AR = 5AP, AS = 5AQ then prove that, SR = 5PQ

Given:
side PQ || side SR
AR = 5AP,
AS = 5AQ
To prove: SR = 5PQ
Proof: In ∆APQ and ∆ARS
∠PAQ = ∠RAS          (Vertically Opposite angles)
∠PQA = ∠RSA          (Alternate angles, side PQ || side SR and QS is a transversal line)
By AA test of similarity
∆APQ ~ ∆ARS

$\frac{}{}$
PQ
SR

=

AP

AR

Corresponding

sides

are

proportional

PQ
SR

=

1

5

AR
=
5
AP

SR
=
5
PQ

Hence proved.

Question 6:

In trapezium ABCD, side AB || side DC, diagonals AC and BD intersect in point O. If AB = 20, DC = 6, OB = 15 then Find OD.

Given:
side AB || side DC
AB = 20,
DC = 6,
OB = 15
In △COD and △AOB
∠COD = ∠AOB         (Vertically opposite angles)
∠CDO= ∠ABO         (Alternate angles, CD ||BA and BD is a transversal line)
By AA test of similarity
△COD ∼ △AOB

$\therefore$

CD
AB

=

OD

OB

Corresponding

sides

are

proportional

6
20

=

OD
15

OD
=
4
.
5

Question 7:

◻ABCD is a parallelogram point E is on side BC. Line DE intersects ray AB in point T. Prove that DE × BE = CE × TE.

Given: ◻ABCD is a parallelogram
To prove: DE × BE = CE × TE
Proof: In ∆BET and ∆CED
∠BET = ∠CED         (Vertically opposite angles)
∠BTE = ∠CDE         (Alternate angles, AT || CD and DT is a transversal line)
By AA test of similarity
∆BET ∼ ∆CED

$\therefore$

BE
CE

=

ET

ED

Corresponding

sides

are

proportional

BE
×
ED
=
CE
×
ET

Hence proved.

Question 8:

In the given figure, seg AC and seg BD intersect each other in point P and

$\frac{}{}$
AP
CP

=

BP

DP

. Prove that, ∆ABP ~ ∆CDP

Given:

$\frac{}{}$
AP
CP

=

BP

DP

To prove: ∆ABP ~ ∆CDP
Proof: In ∆ABP and ∆DCP

$\frac{}{}$
AP
CP

=

BP

DP

(Given)
∠P = ∠P                   (Common)
By SAS test of similarity

$\frac{}{}$
AP
CP

=

BP

DP

Question 9:

In the given figure, in ∆ABC, point D on side BC is such that, ∠BAC = ∠ADC. Prove that, CA2
= CB × CD

To prove: CA2 = CB × CD
Proof: In ∆ABC and ∆DAC
∠C = ∠C                   (Common)
By AA test of similarity
∆ABC ∼ ∆DAC

$\therefore$

BC
AC

=

AC
DC

Corresponding

sides

are

proportional

AC
2

=
BC
×
DC

Hence proved.

Question 1:

The ratio of corresponding sides of similar triangles is 3 : 5; then Find the ratio of their areas.

Question 2:

If ∆ABC ~ ∆PQR and AB : PQ = 2 : 3, then fill in the blanks.

$\frac{}{}$

A

ABC

A

PQR

=

AB
2

=

2
2

3
2

=

Given:
∆ABC ~ ∆PQR
AB : PQ = 2 : 3
According to theorem of areas of similar triangles “When two triangles are similar, the ratio of areas of those triangles is equal to the ratio of the squares of their corresponding sides”.

$\therefore$

A

ABC

A

PQR

=

AB
2

PQ
2

=

2
2

3
2

=

4

9

Question 3:

If ∆ABC ~ ∆PQR, A (∆ABC) = 80, A (∆PQR) = 125, then fill in the blanks.

$\frac{}{}$

A

ABC

A

.

.

.

.

=

80
125

AB
PQ

=

Given:
∆ABC ~ ∆PQR
A (∆ABC) = 80
A (∆PQR) = 125
According to theorem of areas of similar triangles “When two triangles are similar, the ratio of areas of those triangles is equal to the ratio of the squares of their corresponding sides”.

$\therefore$

A

ABC

A

PQR

=

AB
2

PQ
2

80
125

=

AB
2

PQ
2

16
25

=

AB
2

PQ
2

$⇒$

4
2

5
2

=

AB
2

PQ
2

AB
PQ

=

4

5

Therefore,

$\frac{}{}$

A

ABC

A

PQR

=

80
125

and

AB
PQ

=

4

5

Question 4:

∆LMN ~ ∆PQR, 9 × A (∆PQR ) = 16 × A (∆LMN). If QR = 20 then Find MN.

Given:
∆LMN ~ ∆PQR
9 × A (∆PQR ) = 16 × A (∆LMN)
Consider, 9 × A (∆PQR ) = 16 × A (∆LMN)

$\frac{}{}$

A

LMN

A

PQR

=

9
16

MN
2

QR
2

=

3
2

4
2

MN
QR

=

3
4

$⇒$
MN
=

3
4

×
QR

MN
=

3
4

×
20

QR
=
20

MN
=
15

Question 5:

Areas of two similar triangles are 225 sq.cm. 81 sq.cm. If a side of the smaller triangle is 12 cm, then Find corresponding side of the bigger triangle.

According to theorem of areas of similar triangles “When two triangles are similar, the ratio of areas of those triangles is equal to the ratio of the squares of their corresponding sides”.

$\therefore$

Area

of

bigger

triangle

Area

of

smaller

triangle

=

225
81

Side

of

bigger

triangle

2

Side

of

smaller

triangle

2

=

15
2

9
2

Side

of

bigger

triangle

Side

of

smaller

triangle

=

15
9

$⇒$
Side

of

bigger

triangle
=

15
9

×
Side

of

smaller

triangle

Side

of

bigger

triangle
=

15
9

×
12

=
20

Hence, the corresponding side of the bigger triangle is 20.

Question 6:

∆ABC and ∆DEF are equilateral triangles. If A(∆ABC) : A (∆DEF) = 1 : 2 and AB = 4, find DE.

Consider, A(∆ABC) : A (∆DEF) = 1 : 2

$⇒$

A

ABC

A

DEF

=

1
2

AB
2

DE
2

=

1
2

DE
2

=
2

AB
2

$⇒$

DE
2

=
2
×

4
2

AB
=
4

DE
=

32

DE
=
4

2

Question 7:

In the given figure 1.66, seg PQ || seg DE, A(∆PQF) = 20 units, PF = 2 DP, then Find A(◻DPQE) by completing the following activity.

Given:
seg PQ || seg DE
A(∆PQF) = 20 units
PF = 2 DP
Let us assume DP =x

∴ PF = 2x

$\mathrm{DF}$
=
DP
+

PF

=

x

+

2
x

=
3
x

In △FDE and △FPQ
∠FDE = ∠FPQ         (Corresponding angles)
∠FED = ∠FQP         (Corresponding angles)
By AA test of similarity
△FDE ∼ △FPQ

$\therefore$

A

FDE

A

FPQ

=

FD
2

FP
2

=

3
x

2

2
x

2

=

9
4

A

FDE

=

9
4

A

FPQ

=

9
4

×

20

=

45

$\therefore$
A

DPQE

=
A

FDE

A

FPQ

=

45

20

=

25

Question 1:

Select the appropriate alternative.
(1) In ∆ABC and ∆PQR, in a one to one correspondence

$\frac{}{}$
AB
QR

=

BC
PR

=

CA
PQ

then

(A) ∆PQR ~ ∆ABC
(B) ∆PQR ~ ∆CAB
(C) ∆CBA ~ ∆PQR
(D) ∆BCA ~ ∆PQR

(2) If in ∆DEF and ∆PQR, ∠D ≅ ∠Q, ∠R ≅ ∠E then which of the following statements is false?

(A)

$\frac{}{}$
EF
PR

=

DF
PQ

(B)

$\frac{}{}$
DE
PQ

=

EF
RP

(C)

$\frac{}{}$
DE
QR

=

DF
PQ

(D)

$\frac{}{}$
EF
RP

=

DE
QR

(3) In ∆ABC and ∆DEF ∠B = ∠E, ∠F = ∠C and AB = 3DE then which of the statements regarding the two triangles is true ?
(A)The triangles are not congruent and not similar
(B) The triangles are similar but not congruent.
(C) The triangles are congruent and similar.
(D) None of the statements above is true.

(4) ∆ABC and ∆DEF are equilateral triangles, A (∆ABC) : A (∆DEF) = 1 : 2
If AB = 4 then what is length of DE?
(A)

$2$

2

(B) 4
(C) 8
(D)

$4$

2

(5) In the given figure, seg XY || seg BC, then which of the following statements is true?

(A)

$\frac{}{}$
AB
AC

=

AX
AY

(B)

$\frac{}{}$
AX
XB

=

AY
AC

(C)

$\frac{}{}$
AX
YC

=

AY
XB

(D)

$\frac{}{}$
AB
YC

=

AC
XB

(1)
Given:

$\frac{}{}$
AB
QR

=

BC
PR

=

CA
PQ

By SSS test of similarity
∆PQR ~ ∆CAB
Hence, the correct option is (B).

(2)
In ∆DEF and ∆PQR
∠D ≅ ∠Q
∠R ≅ ∠E
By AA test of similarity
∆DEF~ ∆PQR

$\therefore$

DE
PQ

=

EF
QR

=

DF
PR

Corresponding

sides

of

similar

triangles

are

proportional

$\therefore$

DE
PQ

EF
RP

Hence, the correct option is (B).

(3)
In ∆ABC and ∆DEF
∠B = ∠E,
∠F = ∠C
By AA test of similarity
∆ABC ~ ∆DEF
Since, there is not any congruency criteria like AA.
Thus, ∆ABC and ∆DEF are not congruent.
Hence, the correct option is (B).

(4)
Given: ∆ABC and ∆DEF are equilateral triangles
Constrcution: Draw a perependicular from vertex A and D on AC and DF in both triangles.

In ∆ABX and ∆DEY
∠B = ∠C = 60             (∆ABC and ∆DEF are equilateral triangles)
∠AXB = ∠DYB           (By construction)
By AA test of similarity
∆ABX ~ ∆DEY

$\therefore$

AB
DE

=

AX
DY

Corresponding

sides

of

similar

triangles

are

proportional

$\therefore$

DE
PQ

EF
RP

$\frac{}{}$

A

ABC

A

DEF

=

1
2

1
2

×
AB
×
AX

1
2

×
DE
×
DY

=

1
2

AB
2

DE
2

=

1

2

AB
DE

=

AX
DY

DE
2

=
32

DE
=
4

2

Hence, the correct option is (D).

(5)
Given: seg XY || seg BC
By basic proportionality theorem

$\frac{}{}$
AX
BX

=

AY
YC

BX
AX

+
1
=

YC
AY

+
1

BX
+
AX

AX

=

YC
+
AY

AY

$⇒$

AB
AX

=

AC
AY

AB
AC

=

AX
AY

Hence, the correct option is (D).

Question 2:

In ∆ABC, B – D – C and BD = 7, BC = 20 then Find following ratios.

(1)

$\frac{}{}$

A

ABD

A

(2)

$\frac{}{}$

A

ABD

A

ABC

(3)

$\frac{}{}$

A

A

ABC

Question 3:

Ratio of areas of two triangles with equal heights is 2 : 3. If base of the smaller triangle is 6 cm then what is the corresponding base of the bigger triangle ?

$\frac{}{}$

Area

of

smaller

triangle

Area

of

bigger

triangle

=

2
3

1
2

×

Height

of

smaller

triangle
×
Base

of

smaller

triangle

1
2

×
Height

of

bigger

triangle
×
Base

of

bigger

triangle

=

2

3

6

Base

of

bigger

triangle

=

2

3

$⇒$
Base

of

bigger

triangle
=

3

2

×
6

=
9

Question 4:

In the given figure, ∠ABC = ∠DCB = 90° AB = 6, DC = 8 then

$\frac{}{}$

A

ABC

A

DCB

=
?

Given:
∠ABC = ∠DCB = 90°
AB = 6
DC = 8

$\mathrm{Now}$
,

A

ABC

A

DCB

=

1
2

×
AB
×
BC

1
2

×
DC
×
BC

=

6

8

=

3

4

Question 5:

In the given figure, PM = 10 cm A(∆PQS) = 100 sq.cm A(∆QRS) = 110 sq.cm then Find NR.

Given:
PM = 10 cm
A(∆PQS) = 100 sq.cm
A(∆QRS) = 110 sq.cm

$\mathrm{Now}$
,

A

PQS

A

QRS

=

100
110

1
2

×
PM
×
QS

1
2

×
RN
×
QS

=

10
11

$⇒$

10

RN

=

10
11

RN
=
11

cm

Question 6:

∆MNT ~ ∆QRS. Length of altitude drawn from point T is 5 and length of altitude drawn from point S is 9. Find the ratio

$\frac{}{}$

A

MNT

A

QRS

.

The areas of two similar triangles are proportional to the squares of their corresponding altitudes.

$\therefore$

A

MNT

A

QRS

=

5
9

2

=

25
81

Question 7:

In the given figure, A – D– C and B – E – C seg DE || side AB If AD = 5, DC = 3, BC = 6.4 then Find BE.

Given:
DC = 3,
BC = 6.4
In △ABC,  DE || AB

$\therefore$

CD
DA

=

CE
EB

By

basic

proportionality

theorem

3

5

=

6
.
4

x

x

3
x
=
32

5
x

​​

$⇒$
8
x
=
32

x
=
4

Question 8:

In the given figure, seg PA, seg QB, seg RC and seg SD are perpendicular to line AD. AB = 60, BC = 70, CD = 80, PS = 280 then Find PQ, QR and RS.

Given:
AB = 60,
BC = 70,
CD = 80,
PS = 280
Now, AD = AB + BC + CD
= 60 + 70 + 80
= 210
By intercept theorem, we have

$\frac{}{}$
PQ
AB

=

QR
BC

=

RS
CD

=

PS

PQ

60

=

QR

70

=

RS

80

=

280

210

PQ

60

=

QR

70

=

RS

80

=

4

3

$\therefore$
PQ
=

4

3

×
60
=
80

QR
=

4

3

×
70
=

280
3

RS
=

4

3

×
80
=

320
3

Question 9:

In ∆PQR seg PM is a median. Angle bisectors of ∠PMQ and ∠PMR intersect side PQ and side PR in points X and Y respectively. Prove that XY || QR.

In △PMQ, ray MX is bisector of △PMQ.

$\therefore$

PX

XQ

=

MQ

MP

………. (I) theorem of angle bisector.
In △PMR, ray MY is bisector of△PMR.

$\therefore$

PY

YR

=

MR

MP

………. (II) theorem of angle bisector.
But

$\frac{}{}$
MP
MQ

=

MP
MR

……… M is the midpoint QR, hence MQ = MR.

$\therefore$

PX
XQ

=

PY
YR

∴XY || QR ………. converse of basic proportionality theorem.

Question 10:

In the given fig, bisectors of ∠B and ∠C of ∆ABC intersect each other in point X. Line AX intersects side BC in point Y. AB = 5, AC = 4, BC = 6 then find

$\frac{}{}$
AX
XY

.

In △ABY, ∠YBX = ∠XBA

$\frac{}{}$
AX
XY

=

AB
BY

.
.
.

I

By

angle

bisector

theorem

In △ACY, ∠YCX = ∠XCA

$\frac{}{}$
AX
XY

=

AC
CY

.
.
.

II

By

angle

bisector

theorem

From (I) and (II)

$\frac{}{}$
AC
CY

=

AB
BY

AC

BC

BY

=

AB
BY

4

6

BY

=

5
BY

$⇒$
4
BY
=
30

5
BY

9
BY
=
30

BY
=

10
3

From (I), we have

$\frac{}{}$
AX
XY

=

5

10
3

=

3
2

Question 11:

In ▢ABCD, seg AD || seg BC. Diagonal AC and diagonal BD intersect each other in point P. Then show that

$\frac{}{}$
AP
PD

=

PC
BP

Given: ▢ABCD is a parallelogram
To prove:

$\frac{}{}$
AP
PD

=

PC
BP

Proof: In △APD and △CPB
∠APD = ∠CPB         (Vertically opposite angles)
∠PAD = ∠PCB         (Alternate angles, AD || BC and BD is a transversal line)
By AA test of similarity
△APD ∼ △CPB

$\therefore$

AP
PC

=

PD

PB

Corresponding

sides

are

proportional

AP
PD

=

PC

PB

Hence proved.

Question 12:

In the given fig, XY || seg AC. If 2AX = 3BX and XY = 9. Complete the activity to Find the value of AC.

Given:
XY || seg AC
2AX = 3BX
XY = 9
Consider, 2AX = 3BX

$\therefore$

AX
BX

=

3

2

AX
+
BX

BX

=

3

+

2

2

.
.
.
.
.
by

componendo

$\frac{}{}$
AB
BX

=

5

2

.
.
.
.

I

BCA
~

BYX

.
.
.

SAS

test

of

similarity

BA
BX

=

AC
XY

.
.
.
corresponding

sides

of

similar

triangles

5

2

=

AC
9

AC
=

17
.
5

.
.
.
from

I

Question 13:

In the given figure, the vertices of square DEFG are on the sides of ∆ABC. ∠A = 90°. Then prove that DE2
= BD × EC (Hint : Show that ∆GBD is similar to ∆CFE. Use GD = FE = DE.)

Given: ▢DEFG is a square
To prove: DE2 = BD × EC
Proof: In △GBD and △AGF
∠GDB = ∠GAF =  90°         (Given)
∠AGF = ∠GBF                    (Corresponding, GF || BC and AB is a transversal line)
By AA test of similarity
△GBD ∼ △AGF                         …(1)
In △CFEand △AGF
∠FEC = ∠GAF =  90°         (Given)
∠FCE = ∠AGF                   (Corresponding, GF || BC and AC is a transversal line)
By AA test of similarity
△CFE ∼ △AGF                          …(2)
From (1) and (2), we get
△CFE ∼ △GBD

$\therefore$

CE
GD

=

FE

BD

Corresponding

sides

are

proportional

CE
DE

=

DE

BD

GD
=
FE
=
DE

DE
2

=
BD
×
CE

Hence proved.

View NCERT Solutions for all chapters of Class 10

What is the Value of X Given That Pq Bc

Sumber: https://www.meritnation.com/maharashtra-class-10/math/mathematics-part-ii-solutions-/similarity/textbook-solutions/91_1_3385_24433

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