SOLUTION: A small heating unit takes 8 hours longer to melt a piece of iron than does a larger unit. Working together, the heating units can melt the iron in 3 hours. How long would it take

Question 447072: A small heating unit takes 8 hours longer to melt a piece of iron than does a larger unit. Working together, the heating units can melt the iron in 3 hours. How long would it take each heating unit, working alone, to melt the iron?
Answer by jorel1380(3719) (Show Source): You can put this solution on YOUR website!
1/x+1/(x+8)=1/3
3x+24+3x=x2+8x
x2+2x-24=0
(x+6)(x-4)=0
x=-6 or 4
Throwing out the negative answer, we get the larger unit needing 4 hours to melt the iron, and the smaller unit needing 12 hours..
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