1/30 + 1/40 = 7/120
120/7 = 17 1/7 days
Ravi can do a piece of work in 30 days while Prakash can do it in 40 days. In how many days will they finish it together?
  - 19 1/7 days
  - 16 1/7 days
  - 14 1/7 days
  - 17 1/7 days
  - 13 1/7 days