A man completes 7/8 of a job in 21 days. How many more days will it take him to finish the job if quantum of work further increased by 50% ?

Here's a brief, clear explanation: 1. **Calculate the man's work rate:** The man completes 7/8 of a job in 21 days. This means to complete the full original job (8/8), he would take (21 days / 7) * 8 = 3 * 8 = 24 days. So, his work rate is 1/24 of the original job per day. 2. **Calculate the new total quantum of work:** The original quantum of work (let's consider it as 1 unit) is increased by 50%. New total work = 1 * (1 + 50/100) = 1 * 1.5 = 1.5 units. 3. **Calculate the remaining work:** Work already completed = 7/8 of the original job = 7/8 units. Remaining work = New total work - Work already completed Remaining work = 1.5 - 7/8 = 3/2 - 7/8 = (12 - 7) / 8 = 5/8 units. 4. **Calculate the time to finish the remaining work:** Time = Remaining Work / Work Rate Time = (5/8 units) / (1/24 units per day) Time = (5/8) * 24 = 5 * 3 = 15 days. Therefore, it will take him 15 more days to finish the job. The final answer is D) 15.