A and B separately can build a wall in 12 and 16 days, respectively. If they work for 1 day alternatively. Starting with A, in how many days will the wall be built?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e 
days.
| Understanding/Application |
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Let the total work to be done be x. Number of days in which A build the wall = 12 days Work done by A in 1 day = x/12 Number of days in which B build the wall = 16 days Work done by B in 1 day = x/16 |
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Work done in 2 days by A and B working alternatively = x/12 + x/16 = 7x/48 Work done by A and B in 12 days working alternatively for 1 day = (7x/48) × (12/2) = 7x/8 Remaining work after 12 days = x - 7x/8 = x/8 Remaining work after A worked for 13th day = x/8 - x/12 = x/24 The remaining work x/24 will be completed B. Number of days required by B to complete x/24 = (x/24)/(x/16) = 2/3 days Number of days required to complete work = 12 + 1 + (2/3) = 13(2/3) days |