SOLUTION: Hi I can't seem to get the exact answer on this one. The length of each side of a square with an area of 1600 square inches is increased by 20 inches. What is the resulting area

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Question 591442: Hi I can't seem to get the exact answer on this one.
The length of each side of a square with an area of 1600 square inches is increased by 20 inches. What is the resulting area?
I tried all sorts of things, but I just can get it right.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = the length of a side in inches
Let +a+ = the increase in area in in2 when +s+
is increased by +20+
given:
(1) +%28+s+%2B+20+%29%2A%28+s+%2B+20+%29+=+1600+%2B+a+
(2) +s%5E2+=+1600+
-----------------
(1) +s%5E2+%2B+40s+%2B+400+=+1600+%2B+a+
(1) +s%5E2+%2B+40s+-+1200+=+a+
and
(2) +s%5E2+=+1600+
(2) +s+=+40+
Substitute this into (1)
(1) +1600+%2B+40%2A40+-+1200+=+a+
(1) +a+=+1600+%2B+1600+-+1200+
(1) +a+=+3200+-+1200+
(1) +a+=+2000+
The resulting area is +1600+%2B+2000+=+3600+ in2
check:
(1) +%28+s+%2B+20+%29%2A%28+s+%2B+20+%29+=+1600+%2B+a+
(1) +%28+40+%2B+20+%29%2A%28+40+%2B+20+%29+=+1600+%2B+2000+
(1) +60%5E2+=+3600+
(1) +3600+=+3600+