Question

Rain water which falls on a flat surface of length 6m and breadth 4m is transferred into a cylindrical vessel of internal radius 20cm . What will be the height of water in the cylindrical vessel if the rain fall is 2cm ? Give your answer to the nearest whole number. (Use pie=3.14)

Answer 1

dimension of flat surface = 6m×4m or 600cm×400cm
height of rainfall = 2cm
volume of water = 600×400×2 cm³

radius of cylinder = 20cm
let height of water = h
volume = πr²h 

$\pi r^2h=600 \times 400 \times 2\\ \\ \Rightarrow 3.14 \times 20^2 \times h=600 \times 400 \times 2\\ \\ \Rightarrow h= \frac{600 \times 400 \times 2}{3.14 \times 20^2} \\ \\ \Rightarrow h=382.16\ cm\\ \\ \Rightarrow h =\boxed{382\ cm}$

Height of water is 382cm (to the nearest whole number.)

Answer 2

dimension of flat surface = 6m×4m or 600cm×400cm

height of rainfall = 2cm

volume of water = 600×400×2 cm³

radius of cylinder = 20cm

let height of water = h

volume = πr²h