Answer:
The dimensions of the envelope are 5 by 10 inches.
Step-by-step explanation:
Perimeter formula for a rectangle: P = 2W + 2L
Area formula ' " " A = W*L
Here, P = 2W + 2L, so 30 in = 2W + 2L, or 15 in = W + L
Also, A = W*L, so 50 in^2 = W*L, or (if we solve this for W) W = (50 in)/L
But 15 = W + L, or 15 - L = W. Substitute this result for W in the equation W = (50 in)/L:
We get (50 in)/L = 15 - L
Multiplying both sides by L eliminates the fraction:
50 in = 15L - L^2, or
L^2 - 15L + 50 = 0
This factors into (L - 10)(L - 5) = 0, so L is either 10 or 5. Because 15 - L = W, W is either 10 or 5.
The dimensions of the envelope are 5 by 10 inches.
