Working independently, Salam can perform a certain task in 6 hours and Tonny can perform it in 7 hours. If Salam and Tonny work together for 3 hours, and then Salam leaves, how many hours will it take Tonny to complete the task alone?
Explanation: Salam's rate of work = 1/6 and that of Tonny = 1/7. Together their rate of work = \(1/6 + 1/7 = 13/42\). Working together for 3 hours they complete \(3 \times (13/42) = 13/14\) parts of the work. So, remaining work = \(1 - 13/14 = 1/14\). So, Tonny will take \((1/14) / (1/7) = 1/2\) hours to complete the work.
