Question

If a pipe fills the tank in $10$ minutes, how much minutes it will take to half fill the tank in we connect two pipes?

• A. $20$
• B. $10$
• C. $5$
• D. $2.5$

Answer 1

The correct option is D $2.5$

No of pipe (P) is inversely proportional to time (t)
$\Rightarrow P\propto \frac{1}{t}$
But here it takes $10$ minutes to fill the tank.
To half fill the tank the pipe will take $\frac{10}{2}=5minutes$.
Now, $P_1{t}_1=P_2{t}_2$
$P_1=1,t_1=5,P_2=2$, we have to find $t_2$.
$\Rightarrow t_1=\frac{P_1{t}_1}{P_2}=\frac{1\times 5}{2}=2.5minutes$