SOLUTION: please answer my question: Suppose you have 10 kg of cement, 5 kg of gravel, and 5 kg of sand for making concrete. Your concrete should contain 25% water by mass. How much water

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Question 164585: please answer my question:
Suppose you have 10 kg of cement, 5 kg of gravel, and 5 kg of sand for making concrete. Your concrete should contain 25% water by mass. How much water should you add?
Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=amount of water needed
Total weight of the mixture=10+5+5+x=20+x
And we are told that the water equals 25% of the mixture, so:
0.25(20+x)=x get rid of parens (distributive law)
5+0.25x=x subtract 0.25x from each isde
5+0.25x-0.25x=x-0.25x collect like terms
5=0.75x divide each side by 0.75
x= 6.6667 or 6 2/3 kg----------------------amount of water needed
CK
20+6.6667=26.6667
0.25*26.66667= 6.6667
6.6667=6.6667
Hope this helps---ptaylor