Question

how many cubic metres of earth must be dug out to construct a well 7m deep and of diameter 2. 8m

Answer 1

Height = 7m and Diameter = 2.8m

Find Radius:

Radius = Diameter ÷ 2

Radius = 2.8 ÷ 2 = 1.4 m

Find volume:

Volume = πr²h

Volume = π(1.4)²(7) = 43.12 m³

Answer: 43.12 m³ of earth needs to be dug out.

Answer 2

$\bold {\huge {Solutions :-}}$

$\bold {\underline {We~have, }}$

$\bold {Height = 7m}$
$\bold {Diameter = 2.8m}$

$\bold {\underline {Now, }}$

$\bold {Radius = Diameter/2}$

$\bold {= 2.8/2 = 1.4 m}$

$\bold {Volume =}$ π$\bold {r^2 h}$

$\bold { = }$π$\bold {(1.4)^2 (7) = 43.12 m^3 }$

$\bold {\underline {Hence, }}$
$\bold {43.12~ m^3 ~of~ earth~ needs}$
$\bold { to~ be~ dug~ out.}$