Pipes and Cisterns Practice Test 1 with solutions

Part of tank filled by A in 1 minute = $\frac{1}{32}$
Part of tank filled by A in 8 minutes = $8\times \frac{1}{32}$ = $\frac{1}{4}$
Remaining portion of tank need to be filled = $1-\frac{1}{4}$ = $\frac{3}{4}$
Portion of the tank filled by A and B in 1 minute
= $\frac{1}{32}+\frac{1}{28}$ = $\frac{7+8}{224}$ = $\frac{15}{224}$
Time taken to fill $\frac{15}{224}$ th part of the tank = 1 minute
Time taken to fill $\frac{3}{4}$ th part of the tank
= $1\times \frac{224}{5}\times \frac{3}{4}$
= $\frac{56}{4}$ = $11\frac{1}{5}$ minutes.