Answer:
The pipe A will fill the pool in 2.25 hours and the pipe B will fill the pool in 1.75 hours.
Step-by-step explanation:
Pipe A alone can fill the pool in 4 hours.
So, in 1 hour it fills [tex]\frac{1}{4}[/tex] part of the pool.
and in 30 minutea it fills [tex]\frac{1}{8}[/tex] part of the pool.
If the pipe B is opened after 30 minutes the pipe A opened.
So, [tex](1-\frac{1}{8} ) =\frac{7}{8}[/tex] part of the pool is filled by both the pipe.
Again, pipe B alone fills the pool in 4 hours.
Hence, if both the pipes are open then they will fill in one hour [tex](\frac{1}{4} +\frac{1}{4}) =\frac{1}{2}[/tex] part of the pool.
So, the remaining [tex]\frac{7}{8}[/tex] part of the pool will be filled by both the pipe in [tex]\frac{\frac{7}{8} }{\frac{1}{2} } =\frac{7}{4}[/tex] hours i.e. 1.75 hours.
Therefore pipe A will fill the pool in (0.5 + 1.75) =2.25 hours and pipe B will fill the pool in 1.75 hours. (Answer)
