Sonu can do a work in 15 days, Monu can do it in 10 days, and Tipu can do it in 12 days. In how many days can Sonu, Monu and Tipu together complete the work?

4 days

Sonu = 15 days, Monu = 10 days, Tipu = 12 days,

⇒ Time required by Sonu + Monu + Tipu to complete the work = \(\frac{60}{4+6+5}\) = \(\frac{60}{15}\) = 4 days,    ..(\(\frac{Work}{Efficiency}\) = Time)