Pradeep can do a piece of work in 24 days, Sanu in 52 days and Kanhaiya in 64 days. All begin to do it together but Pradeep leaves after 6 days and Sanu leaves 6 days before the completion of the work. How many days did the work last ?

25 days (approx)

Total efficiency of (P + S + K) = 191R

They worked for 6 days before Pradeep leaves

i.e. work done = 191R × 6 = 1146R unit

Remaining work = 2496R - 1146R = 1350R units

Now Sanu left Kanhaiya alone for 6 days, so Kanhaiya alone did 6 days work

i.e. work done = 39R × 6 = 234R units

Remaining work = 1350R - 234R = 1116R units

The remaining work was done by both Sanu and Kanhaiya

So, days taken by (Sanu + Kanhaiya) = \(\frac{1116}{87}\) = 12.82

Total days taken = 6 + 6 + 12.82 = 24.82

                         = 25 (approx)