UP Police Constable Exam Model Paper 3

Here work is the volume of the wall. If L, B, H are length, breadth and height of the wall respectively and M, D and T are men, days and time in hours per day, respectively.
So,
$\frac{{\mathrm{M}}_1{\mathrm{D}}_1{\mathrm{T}}_1}{{\mathrm{L}}_1{\mathrm{B}}_1{\mathrm{H}}_1}=\frac{{\mathrm{M}}_2{\mathrm{D}}_2{\mathrm{T}}_2}{{\mathrm{L}}_2{\mathrm{B}}_2{\mathrm{H}}_2}$
$\Rightarrow \frac{80\times 20\times 8}{160\times 15}=\frac{64\times 40\times 5}{\mathrm{x}\times 20\times 10}$
$\Rightarrow \frac{80\times 8}{160\times 15}=\frac{64}{\mathrm{x}}$
$\Rightarrow \frac{8}{2\times 15}=\frac{64}{\mathrm{x}}$
$\Rightarrow \frac{1}{2\times 15}=\frac{8}{\mathrm{x}}$
∴ x = 240