a tank can be filled using pipes A,B or both. It takes pipe A, running alone 18 hours to feel the tank. It takes both pipes running together 9.9 hours to fill the tank. how long does it take pipe B, running alone, to fill the tank?

Question

mertsj · Answer

$$\frac{1}{18}+\frac{1}{x}=\frac{1}{9.9}$$

anonymous · Answer

so now di I find a common denominator?

mertsj · Answer

Multiply the 3 denominators together.

anonymous · Answer

but they don't equal the same I got 54 and 27.7

anonymous · Answer

29.7 im really confused

mertsj · Answer

$$\frac{1}{18}\times 18(9.9)(x)+\frac{1}{x}\times 18(9.9)(x)=\frac{1}{9.9}\times18(9.9)(x)$$
$$9.9x+18(9.9)=18x$$
$$178.2=8.1x$$

mertsj · Answer

You can finish it.

anonymous · Answer

alright thank you

anonymous · Answer

Alternatively, calculate the two fractions, and take their difference, which will give you 1/x, then use x = 1/(1/x)