A and B have been put into a work to complete it in 40 days. They work for 10 days then they are forced to work with double of their efficiencies. In total how many days work will be completed?
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20 days
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25 days
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30 days
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34 days
B
Correct answer
Explanation
Let total work = 1 unit. A and B together complete in 40 days, so their combined rate = 1/40 per day. In first 10 days, they complete 10 × (1/40) = 1/4 work. Remaining = 3/4. Now their rate doubles to 1/20 per day. Time for remaining = (3/4) ÷ (1/20) = 15 days. Total = 10 + 15 = 25 days.