Asked by Leyley

What is the dimension of a rectangle whos perimeter is 42 inches and its area is 104 square inches? Explain.
Answered by Reiny
2x + 2y = 42
x + y = 21
y = 21-x

xy=104
x(21-x) = 104

expand, simplify and arrange as a quadratic
it factors, if you can't see the factors, use the quadratic formula.
Answered by Reiny
Just noticed you are only grade 7 and probably don't know quadratic equations.

so look at x+y=21 and xy=104
can you think of two numbers that add to get 21 and multiply to get 104

perhaps make a list
#1 #2 product
20 1 20
19 2 38
18 3 54
17 4 68
...
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