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 is further increased by 50% ?

• The man completes 7/8 of the job in 21 days, so his work rate is (7/8) / 21 = 1/24 of the job per day.

• The remaining part of the original job is 1 - 7/8 = 1/8.

• The quantum of work is increased by 50%, so the new total work is 1 + 0.5 = 1.5 times the original job.

• The remaining work to be done is the original remaining 1/8 plus the additional 50% of the total job (0.5 * 1.5 = 0.75), totaling 1/8 + 3/4 = 1/8 + 6/8 = 7/8 of the original job.

• Time required = (Remaining Work) / (Rate) = (7/8) / (1/24) = (7/8) * 24 = 21 days.

• Wait, let me re-read carefully. 'How many more days will it take him to finish the job if quantum of work is further increased by 50%?'

• Let's re-calculate. Rate = 1/24 job/day.

• Current status: 7/8 done. Remaining original: 1/8.

• New total work = 1.5 jobs.

• Work already done = 7/8 of 1 job = 0.875 jobs.

• Remaining work = 1.5 - 0.875 = 0.625 jobs = 5/8 jobs.

• Time = (5/8) / (1/24) = (5/8) * 24 = 15 days.

• Therefore, it will take 15 more days.