+660 60 bricklayers began a 16-day project to build a castle. After five days, five of the bricklayers quit the job. If they work the same amount each day, how many extra day(s) (beyond the original estimate of 16) will the remaining bricklayers need?
You can use proportional relationships:
60 brick-layers -> 16-day project
15/4 brick-layers -> 1-day project
15/4*5 brick-layers -> 5-day project
So the bricklayers will need an extra 5 days.
16 - 5 ==11 days' work remains
11 / 16 - ratio of the work that remains
[60 x 16] / 55 ==17.4545.... what would have taken 55 men to finish the original work.
But only 11 / 16 of the original work remains, therefore:
So:17.454545..... x 11/16 ==12 days that would take 55 men to finish, or 1 extra day.
In total: 5 + 12 ==17 days to finish the work, or 1 extra day due to departure of 5 men.
