Question 58109
To meet the government's specifications, an alloy must be 65% aluminum. How many pounds each of a 70% aluminum alloy and a 54% aluminum alloy will be needed to produce 640 pounds of the 65% aluminum alloy?
:
A typical mixture problem, if you learn this method you will be able to handle most mixture-type problems.
: 
Let x = the amt of the 70% alloy; Since the total will be 640 lb, 
the 54% amt = (640-x)
:
.70x + .54(640-x) = .65(640)
.70x + 345.6 -.54x = 416
.70x - .54x = 416 - 345.6
.16x = 70.4
x = 70.4/.16
x = 440 lb of 70% aluminum
:
640 - 440 = 200 lb of the 54% aluminum
:
:
Check: 
.7(440) + .54(200) = .65(640)
  308 + 108 = 416