P and Q can complete a project in 15 days and 10 days, respectively. They started doing the work together, but after 2 days, Q had to leave and P alone completed the remaining work. In how many days was the whole work completed?

12

P = 15 days

Q = 10 days

⇒ Here, Q worked for 2 days, therefore,

⇒ Work done by Q in 2 days = 3 x 2 = 6        (Efficiency x Time = Work)

Now, Remaining work = 30 - 6 = 24

Here, remaining work done by P in the whole time(including 2 days),

So, time taken by P to do the work = \(\frac{24}{2}\) = 12 days                    (\(\frac{work}{efficiency}\) = Time)

Therefore, the whole work is done in 12 days.