Multiple choice

$A$ and $B$ working together can mow a field in $56$ days and with the help of $C$ , they could have mowed it in $42$ days. How long would $C$ take by himself ?

  1. $168$ days
  2. $180$ days
  3. $151$ days
  4. $140$ days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the work be 1 unit. A+B do 1/56 per day, and A+B+C do 1/42 per day. C's daily rate is (1/42) - (1/56) = (4-3)/168 = 1/168. Thus, C takes 168 days.

AI explanation

Using the sum of their 1-day work rates, A and B together complete 1/56 of the work per day. When A, B, and C work together, they complete 1/42 of the work per day. Subtracting the first rate from the second gives C's 1-day work rate as (1/42 - 1/56) = 1/168. Therefore, C alone would take exactly 168 days to mow the field.

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