Question

If two circles have radii 10 cm and 15 cm and they touch each other
internally, find distance between their centers.​

Answer 1

BO

1

is⊥

r

toAC

∴AB=

2

AC

=

2

12

=6cm

inΔABO

1

andABO

2

byusingpythogorastheorem

AB

2

+BO

1

2

=AO

1

2

BO

1

=

AO

1

2

−AB

2

=

(8)

2

−(6)

2

=

64−36

=

28

unit

and

BO

2

=

AO

2

2

−AB

2

=

(10)

2

−(6)

2

=

100−36

=

64

unit

Thendistancebetweentheircentresis(BO

1

+BO

2

)=

28

+

64

2

7

+8unit