If A can do a job in 10 days, B in 15 days. They work together for 4 days, then A leaves. How many more days for B alone?
5 days
The answer
A rate=1/10, B rate=1/15. Together=1/6/day. In 4 days: 2/3 done. Remaining: 1/3. B alone: (1/3)÷(1/15)=5 days.
Source: Verified
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