Question

A water filter takes 40 minutes to filter 20 litres of water. Another filter of same specifications takes 30 minutes to filter the same amount of water. If both the filters are used at the same time . Then how long it will take them to filter the 70 litres of water.

Answer 1

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Here is the solution:

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A Water filter takes 40 mins to filter 20 litres

⇒ 40 mins = 20 litres

⇒ 1 min = 20 ÷ 40 = 1/2 litres

Another filters takes 30 mins to filter the 20 litres of water

⇒ 30 mins = 20 litres

⇒ 1 min = 20/30 = 2/3 litres

So if both filter works at the same time:

⇒1 min = 1/2 + 2/3 = 7/6 litres

Find the time needed to filter 70 litres of water:

⇒ 7/6 litres = 1 min

⇒ 1 litres = 1 ÷ 7/6 = 6/7 min

⇒ 70 litres =6/7 x 70 = 60 min = 1 hour

Answer: It will take 1 hour to filter 70 litres of water.

Answer 2

here is your answer OK dude

Ans is 3)1 hour
For the first filter,
40 minutes take to fill 20 liters of water.
Therefore,in 1 minute 20/40=1/2 liters of water can be filled.

For the second filter,
30 minutes take to fill 20 liters of water.
Therefore,in 1 minute 20/30=2/3 liters of water can be filled.
So,Two types together can fill in 1 minutes=(1/2+2/3)=7/6 liters.
Now,if 7/6 liters can be filled in 1 minute then,
70 liters can be filled in=(6/7)*70=60 minutes=1 hour.