Multiple choice

A builder appoints three construction workers Akash, Sunil and Rakesh on one ofhis sites. They take 20, 30 and 60 days respectively to do a piece of work. How manydays will it take Akash to complete the entire work if he is assisted by Sunil and Rakeshevery third day?

  1. 10 days

  2. 15 days

  3. 25 days

  4. 30 days

  5. 45 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Akash works at a rate of 1/20 per day. Every third day, Sunil (1/30) and Rakesh (1/60) help, making the combined rate 1/20 + 1/30 + 1/60 = 6/60 = 1/10. In a 3-day cycle, Akash works alone for 2 days (2/20 = 1/10) and with help for 1 day (1/10), totaling 2/10 = 1/5 of the work per cycle. Thus, 5 cycles (15 days) are needed to complete the work.

AI explanation

Using the Least Common Multiple (LCM) method, let the total work be 60 units, making the work rates of Akash, Sunil, and Rakesh 3, 2, and 1 units per day respectively. Akash works alone on the first two days, completing 3 + 3 = 6 units, and on the third day all three work together to complete 3 + 2 + 1 = 6 units, meaning 12 units are completed every 3 days. To finish 60 units, it takes (60 / 12) * 3 = 15 days.

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