If A can do a work in 21 days and B can do the same work in 28 days. In how many days will they complete the work if they work on alternate days?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 24 days.
Let the total work be LCM(28, 21) = 84 units
The work done by A in 1 day = = 4 units
The work done by B in 1 day = = 3 units
The work done in 2 days = 4 + 3 = 7 units
Hence 7 units of work are completed in 2 days
84 units will be completed in = = 24 days.