Question

the curved surface area of a 15 cm high cylinder is 2310 cm^2.A wire of a diameter 6 mm is wound around it so as to cover it completely. find the length of the wire.​

Answer 1

$\large{\underline{\underline{\bold{\red{\sf{Bonjour !}}}}}}$

answer is

20m

1000cm2=2π×radius×height

Let the no. of turns the wire had made on the surface be n.

For n turns, the wire should make upto 5n mm or 0.005n m height

Since the wire should completely cover the cylinder, 

∴ Height of cylinder =0.005n m

Let the length of wire needed be lm

l=2π×radius×n

nl=2π×radius

1000cm2=0.1m2=2π×radius×height

0.1=(nl)×0.005n

l=0.0050.1=20m

$\large{\bold{\blue{\sf{Thanks}}}}$