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Recommended: CSS General Ability 2019 Solved Q (6a) And Q (6c)
Explanation
There are two pipes that fills the pool but speed of efflux of one pipe is 1.25 times the other. When both pipes are used, they take 5 hours to fill the entire pool.
To Find
Time taken by the slower pipe, if only the slower pipe is used to fill the pool = ?
Illustration
Suppose Ali and Saif challenge each other to run the 50km race. The speed of Saif is double as compared to Ali. If Ali finishes it in 10 hours then how long do you think Saif should have taken?
5 Hours
What you did here? Actually, you simply divided 10 over 2 because speed of Saif is double as compared to Ali. In the same way, to solve this problem we will consider (x) the time taken by the slower pipe and divided it over 1.25 for the time taken (x/1.25) by the faster pipe.
Solution
Let,
Time taken by the slower pipe = x
So, the time taken by the faster pipe = x/1.25
Time taken by the both pipe to fill the entire pool = 5 hours
Now, according to the given condition

Conclusion
So, slower pipe would take 11.25 hours to fill the pool.