Question

Below are the drawings of cross sections of two different pipes used to fill swimming pools. Figure A is a combination of 2 pipes each having a radius of 8 cm. Figure B is a pipe having a radius of 15 cm. If the force of the flow of water coming out of the pipes is the same in both the cases, which will fill the swimming pool faster?

Answer 1

In figure A, 2 pipes each having a radius of 8 cm

∵ Area of a circle = πr²

∴ Area of one pipe = `22/7 xx 8 xx 8`

= `(22 xx 8 xx 8)/7`

= `(22 xx 64)/7` cm²

Area of 2 pipes = `(2 xx 1408)/7`

= `2816/7` cm²

= 402.28 cm²

In figure B, a pipe having radius of 15 cm

∴ Area of the pipe = πr²

= `22/7 xx 15 xx 15`

= `22/7 xx 225`

= `4950/7`

= 707.14 cm²

Clearly, the surface area of pipe B is greater. So, pipe B fills the swimming pool faster.