A swimming pool can be filled in 19 hours if water enters through a pipe alone, or in 20 hours if water enters through a hose alone. If water is entering through both the pipe and the hose, how long will it take to fill the pool ?

Question

anonymous · Answer

I know a great strategy

anonymous · Answer

first u would find how much wan done in 1 hour

anonymous · Answer

$$pipe=\frac{ pool }{ 19 h }$$$$hose=\frac{ pool }{ 20 h }$$

$$pipe+hose=\frac{ pool }{ 19 h }+\frac{ pool }{ 20 h }=\frac{ pool \times 20 }{ 19 h \times 20}+\frac{ pool \times 19}{ 20 h \times 19 }$$
$$=\frac{ pool \times 20 + pool \times 19}{ 380 h} =\frac{39pool}{380h}=\frac{pool}{9.74h}.$$Takes 39/380 = 9.75 hours to fill pool using both at the same time.

anonymous · Answer

next take the reciprocal which is  380/39

anonymous · Answer

this is about 9.75