Answer :
630 gallons of 90% antifreeze has to be mixed.
Sum of values of two solutions = Value of mixture
90% =0.9 unit value and amount x we get value 0.9x
10%= 0.1 unit value and amount 90 we get value =0.1*90=9
total mixture =0.80 value x+90 we get value 0.8*(x+90)
0.9x + 9 = 0.8(x + 90)
0.9x + 9 = 0.8x + 90 x 0.8
0.9x – 0.8x = 72 – 9
0.1x = 63
x = 630
Hence, 630 gallons of 90% antifreeze has to be mixed.
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