P and Q together can do a piece of work in 6 days. Q and R can finish the same work in \(\frac{48}{7}\) days. P started the work and worked for 4 days. Q and R continued for 4 days. Then the difference of days in which Q and R can complete the work is?

4 days

Total work = Efficiency × Number of days

(Q + R)'s 4 days work = 7 × 4 = 28

Remaining work = 48 - 28 = 20

This is to be done by P in 4 days

Hence efficiency of P = \(\frac{20}{4}\) = 5 unit/day

 (P + Q) = 8 unit/day

 Q = 8 - 5 = 3 unit/day

 Q + R = 7 unit/day

R = 7 - 3 = 4 unit/day

Q can finish the work in = \(\frac{48}{3}\) = 16 days

R can finish the work in = \(\frac{48}{4}\) = 12 days

Difference = Q - R = 16 -12 = 4 days