Multiple choice

A can do a piece of work in $10$ days , B in $18$ days and A, B and C together in $4$ days. In how many days will C alone can do it?

  1. $ 6\dfrac{2}{3} $
  2. $ 15\dfrac{17}{19} $
  3. $ 10\dfrac{10}{17} $
  4. $ 11\dfrac{9}{4} $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A = 1/10, B = 1/18, A+B+C = 1/4. C = 1/4 - (1/10 + 1/18) = 1/4 - (9/90 + 5/90) = 1/4 - 14/90 = 1/4 - 7/45 = (45 - 28) / 180 = 17/180. Time = 180/17 = 10 10/17 days.

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