Multiple choice

Painter 'A' can paint a house in 10 days and painter 'B' can do the same in 20 days. With the help of 'C', they complete the job in 5 days only. Then, 'C' alone can do the job in

  1. 20 days

  2. 10 days

  3. 40 days

  4. 50 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A's rate = 1/10, B's rate = 1/20. Together A+B+C = 1/5. C = 1/5 - (1/10 + 1/20) = 1/5 - 3/20 = 4/20 - 3/20 = 1/20. C takes 20 days.

AI explanation

Taking the total work as the least common multiple of 10, 20, and 5, which is 20 units, the daily work of A, B, and their combined effort with C are 2 units, 1 unit, and 4 units respectively. The sum of A and B's daily work is 3 units, so C's daily work must be 1 unit (4 minus 3). Therefore, C alone can complete the 20-unit job in 20 days.

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