O, T and P can do a piece of work in 3, 4 and 6 hours respectively. If they are working together, then in how much time they will finish the work?

1 hour 15 minutes 1 hour 10 minutes 1 hour 1 hour 20 minutes

1 hour 20 minutes

O = 3 hours, T = 4 hours, P = 6 hours,  ⇒ So, Time required for O + T + P to complete the work = \(\frac{12}{4+3+2}\) = \(\frac{12}{9}\) =\( {1 }_{ 9}^{3 } \) = \( {1 }_{ 3}^{1 } \) = 1 hours 20 minutes.