Question 765002
Please help me solve this word problem as I don't understand how to solve mixture problems. 
What quantity of 70 per cent acid solution must be mixed with a 25 solution to produce 972 mL of a 50 per cent solution?
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let x=quantity (mL) of 70% solution to be mixed
972-x=quantity (mL) of 25% solution to be mixed
quantity of acid in the two solutions=quantity of acid in the mixture
70%x+25%(972-x)=50%*972
.70x+243-.25x=486
.45x=243
x=540
972-x=432
quantity (mL) of 70% solution to be mixed=540 mL
quantity (mL) of 25% solution to be mixed=432 mL