Question

If two pipes function simultaneously, the reservoir will be filled in 12 hours. One pipe fills the reservoir 10 hours faster than the other. How many hours the faster pipe take to fill the reservoir?

• A. 35 hours
• B. 30 hours
• C. 40 hours
• D. None of these

Answer 1

The correct option is B 30 hours

Let one pipe take x hours to fill the reservoirs

Then, another pipe takes (x - 10) hours

$\therefore \frac{1}{x}+\frac{1}{x-10}=\frac{1}{12}$

$\Rightarrow x(x-10)=12(x+x-10)$

$\Rightarrow x^2-34x+120=0$

$or(x-30)(x-4)=0$

$\therefore x=30orx=4$

$\therefore$ The faster pipe takes 30 hours to fill the reservoir.