water is wasted everyday, then the water last for 50 days only. How many days will the supply

Question

A water tank has sufficient water for 60 days. If 50 litres of water is wasted everyday, then the water last for 50 days only. How many days will the supply last if 350 litres of water is wasted everyday?
A. 8
B. 10
C. 15
D. 25

Answer 1

If you use water efficiently at X amount per day then in 60 days you use 60x. 

Then if you use X+50wasted for 50 days then the amount used is 50(X+50) or 50x+2500 must be the same amount in the tank for 60 days of 60X. So set them equal to each otheR. 

 

50x+2500=60x

so 10x=2500

x=250

 

so 250(60)=15,000 is what the tank holds. 

So if 350 are wasted each day, then 250 are used and 350 are wasted each day so (250+350)=600 each day so 15,000/600 =25 days to use the entire Tank. The answer is D. 

 

 

Answer 2

Let's say that the tank has a total capacity of X liters and the normal daily usage is Y. The first sentence says that X = 60*Y, and the second sentence says that X = 50*(Y+50), since 50 more liters of water are used every day than usual. These expressions are equal, so 60*Y = 50*(Y+50), which can be algebraically rearranged to get 10*Y = 2500. At this point, the hard work is done, and all that remains is to solve for Y, then solve for X, and finally get the answer.