A tank is drained by two pipes. One pipe can empty the tank in 45 mins. while the other can empty in an hour. If the tank is 3/4 filled and both pipes are open , at what time will the tank be emptied?

Question

anonymous · Answer

pls help :) @jojo4eva

anonymous · Answer

pls help @mathmath333

mathmath333 · Answer

when the tank is full

$\large\tt \color{black}{\dfrac{x}{45}+\dfrac{x}{60}=1}$

mathmath333 · Answer

is the answer given in ur book?

anonymous · Answer

No.

anonymous · Answer

doh i mean $${\dfrac{x}{45}+\dfrac{x}{60}=\frac{3}{4}}$$

mathmath333 · Answer

well i think here u have to find the value of x from the equation and multiply it by 3/4


not sure lol

anonymous · Answer

you could be right,

mathmath333 · Answer

$\large\tt \color{black}{\ddot\smile}$

anonymous · Answer

their combined rate is 
$$\frac{1}{60}+\frac{1}{45}$$ and you want to solve 
$$(\frac{1}{60}+\frac{1}{45})t=\frac{3}{4}$$ for $t$

anonymous · Answer

$$\frac{64+45}{60\times 45}t=\frac{3}{4}$$
$$t=\frac{3}{4}\times\left(\frac{60\times 45}{60+45}\right)$$