If 20 men can complete a piece of work in 18 days working 5 hours per day, in how many days can 25 men complete it, working 6 hours per day?

12 days

Formula to be used here,

\( { M}_{1 } \) x \( { D}_{1 } \) x \( { H}_{1 } \)  = \( { M}_{2 } \) x \( { D}_{2 } \) x \( { H}_{2 } \)

where, M = No. of Men, D = No. of Days, H = No. of Hours,

⇒ 20 x 18 x 5 = 25 x \( { D}_{2 } \) x 6

⇒ \( { D}_{2 } \) = 12 days,