Every day one man can do 1 / ( 28 60 ) = 1 / 1620 of a job.
After 15 days:
( 28 15 ) / 1620 = 1 / 4
From the 16 th to the 45 th day:
( 23 30 ) / 1620 = 23 / 56
1 /4 + 23 / 56 + ( 33 x ) / 1620 = 1
14 / 56 + 23 / 56 + 11 x / 560 = 1
140/ 560 + 230 / 560 + 11 x / 560 = 1
370 + 11 x = 560
11 x = 190
x = 190 : 11 ≈ 17.27
17.27 - 15 = 2.27 days
Answer: 3 days were delayed in finishing the job.
