P, Q and R can do a piece of work in 100, 75 and 25 days respectively. P is assisted by Q on one day and R on the next day alternatively. How long would the work take to finish ?
Answer & explanation
Correct answer: option 4
( P + Q )'s 1 day work = 3 + 4 = 7
( Q + R )'s 1 day work = 3 + 12 = 15
2 days work = 15 + 7 = 22 unit
2 days ------- 22 unit
but total work to be done is 300 unit so multiply 22 by \(\frac{150}{11}\)
similarly number of days = 2 × \(\frac{150}{11}\)
= 27\(\frac{3}{11}\) days