SOLUTION: You currently have 325 lb of a cement mixture containing 18.0% sand by mass. How much sand must you add to create a mixture that is 25.0% sand by mass?

Question 1204766: You currently have 325 lb of a cement mixture containing 18.0% sand by mass.
How much sand must you add to create a mixture that is 25.0% sand by mass?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
You currently have 325 lb of a cement mixture containing 18.0% sand by mass.
How much sand must you add to create a mixture that is 25.0% sand by mass?

You currently have 325 lb of a cement mixture containing 18.0% sand =58.5 lbs sand
Assume we add x lbs of sand
58.5+x = (325+x)*0.25
58.5+x = 81.25 +0,25x
x-0.25x = 81.25-58.5=22.75
0.75x=22.75
x= 22.75/0.75= 30.33 approx
Check
Total Sand / Total mix
(58.5+30.33)/(325+30.33) =0.2499 = 24.99 %

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