A work can be completed by 20 men in 50 days. 30 more men join them after 10 days of work. How many days will be saved in completion of the work?

24 days

Formula to be used here,

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

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

⇒ Putting in the values, 

⇒ 20 x 40 = 50 x \( { D}_{2 } \)

⇒ \( { D}_{2 } \) = 16 days,

Therefore, No. of Days saved = 40 - 16 = 24 days,