30 men working 8 hours per day can dig a pond in 16 days. By working how many hours per day can 32 men dig the same pond in 20 days?

6 5 7 8

6

⇒ Efficiency × Days = Total work ⇒ \(\frac{M_1\;×\;D_1\;×\;H_1}{E_2\;×\;D_2\;×\;H_2}\) = \(\frac{W_1}{W_2}\) ATQ, ⇒ \(\frac{30\;×\;16\;×\;8}{32\;×\;20\;×\;H_2}\) = \(\frac{1}{1}\) ⇒ H2 = 6 hours per days