Question

[32] Two concentric circles are of radii 5 cm and 3cm.Find the length of the chord of the larger circle
which touches the smaller circle.

[33] 2 cube seach of volume 64 cm 3 are joined end to end.Find the surface area of the resulting cuboid.

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Answer 1

Answer:

Let PQ be the chord of the larger circle which touches the smaller circle at the point L. Since PQ is tangent at the point L to the smaller circle with centre O.Thus

OL=3 cm and OP=5 cm

∴OL⊥PQ

Since PQ is a chord of the bigger circle and OL⊥PQ

∴OL bisects PQ

∴PQ=2PL

In right angled △OPL

PL=

OP

2

−OL

2

=

5

2

−3

2

=

25−9

=

16

=4 cm

∴ Chord PQ=2PL=2(4)=8 cm

Hence length of the chord PQ=8 cm.

solution

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