Multiple choice

A can do a work in 15 days, B can do it in 12 days but C can do (\frac{3}{4})th of the work in 18 days. Find the time taken by all together to complete the whole work.

  1. $4(\frac{7}{15}) days$
  2. $5(\frac{5}{23}) days$
  3. $6(\frac{3}{19}) days$
  4. $4(\frac{13}{25}) days$

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A's rate: 1/15 work/day. B's rate: 1/12 work/day. C does 3/4 work in 18 days, so full work in 24 days, rate = 1/24. Combined rate = 1/15 + 1/12 + 1/24 = 8/120 + 10/120 + 5/120 = 23/120. Time = 120/23 = 5(5/23) days.

Keep practicing — related questions