Question

9. A toy consists of 14 plastic circular rings
of different radii. The radius of the smallest
ring is 1 cm, the radius of the ring larger
than that is 2 cm and so on. The radius
of the largest ring is 14 cm. Find the sum
of circumferences of all these 14 rings.
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Answer 1

Answer:The disks are increasing in AP

circumference=2*π*r

Sum=2*π*1cm+2*π*2cm......................2*π*14cm

This is an AP

a=2π

d=4π-2π

=2π

n=14

Sn=n/2*[2a+(n-1)d]

=14/2*[2*2π+13*2π]

=7*[4π+26π]

=7*30π

=7*30*22/7

=30*22

=660

The answer is 660cm

Hope it helps.

Step-by-step explanation:

Answer 2

Answer:

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