SOLUTION: A certain job requires 56 pieces of round stock, some 9 inches long and some 7 inches long. If the total length of round stock required is 456 inches, find the number of 9 inch and

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Question 882163: A certain job requires 56 pieces of round stock, some 9 inches long and some 7 inches long. If the total length of round stock required is 456 inches, find the number of 9 inch and 7 inch pieces needed.
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
A certain job requires 56 pieces of round stock, some 9 inches long and some 7 inches long.
If the total length of round stock required is 456 inches, find the number of 9 inch and 7 inch pieces needed.
:
Let a = no. of 9" stock
let b = no. of 7" stock
:
Two equations
a + b = 56
9a + 7b = 456
:
Rearrange the 1st euation for substitution
a + b = 56
a = (56 - b)
:
In the 2nd equation replace a with (56-b)
9(56-b) + 7b = 456
504 - 9b + 7b = 456
-2b = 456 - 504
-2b = -48
b = +24 of the 7"
I'll let you find a, check your solutions in the 2nd equation