Quantitative Aptitude • Time, Speed & WorkEasy
A can finish a piece of work in 20 days and B can finish it in 60 days. How many days will they take working together?
A. 17 days
B. 15 days✓ Correct Answer
C. 80 days
D. 40 days
💡 Solution & Explanation
In one day A does 1/20 of the work and B does 1/60. Together they do 1/20 + 1/60 = 1/15 of the work per day. So the whole work takes 15 days. Shortcut: ab ÷ (a + b) = 1200 ÷ 80 = 15. Together they must be faster than either one alone.
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