A can do a certain work in 15 days, while B can do the same work in 21 days. If they work together, then in how many days will the same work be completed?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 8
Concept used:
LCM method is used.
Calculations:
Let the total work done by A and B be 105 units (LCM of 15 and 21)
Work done by A in 1 day = 105/15 = 7 units
Work done by B in 1 day = 105/21 = 5 units
Total work done by A and B in 1 day = 12 units
Required time taken = 105/12 =