Time and Work Practice Test 1 with solutions

Work done by 90 workers in 1 day = $\frac{1}{360}$
Work done by 90 workers in 90 days
= $90\times \frac{1}{360}$ = $\frac{1}{4}$
Remaining work 1 - $\frac{1}{4}$ = $\frac{3}{4}$
90 more workers have joined, so total workers = 180
If 90 workers finish work in 360 days, then 180 workers finish the work in 180 days
So, $\frac{3}{4}$ th part of work is done by 180 workers in
$180\times \frac{3}{4}$ = 135 days.
Time taken to complete the work = 90 + 135 = 225
Number of days saved = 360 - 225 = 135 days.