Question

if 28 pumps can empty hours reservoir in 18 hours, how long will 35 pumps take to do the same work? ​

Answer 1

Answer:

14.4h

Step-by-step  

28*18/35=14.4

Answer 2

Hello there!

If 28 pumps take 18 hours together, then 1 pump alone must take way more time than 18 hours.

Therefore, time taken by one pump is equal to $18\times28$. Do not evaluate the value now, as you can perform cancellation later.

Now, we need to calculate how much time 35 pumps will take. As we can see, if there are more pumps, then less time is taken. So, this is an inverse relation.

To find the time taken by 35 pumps, divide $18\times28$ with $35$, which will give:

$= \dfrac{18\times28}{35}$

$= 18\times\dfrac{28}{35}$

$= 18\times\dfrac{4}{5}$

$= 14.4$ hours.

That's it! It's really simple.

Points/concepts to remember:

1. Proper and logical identification of type of proportion, direct or inverse.
2. Keeping an eye for places where you can possibly perform cancellation (for example, division)