Which of the following are the dimensions of a rectangle with the perimeter of 26 cm and an area of 42 square cm?
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Which of the following are the dimensions of a rectangle with the perimeter of 26 cm and an area of 42 square cm?
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this can be solved using simple arithmetic
half the perimeter is (1/2)*(26)=13
find two numbers that add up to 13 and multiply to make 40
8 and 5 are the numbers
26=2*8+2*5
26=16+10
26=26
A=8*5
A=40 square cm
you can do all the algebra you want but it comes down to what I wrote
26=2l+2w
13=l+w
l=13-w
A=lw
40=(13-w)(w)
40=13w-w^2
w^2-13w+40=0
factor (what 2 numbers multiply to make 40 and add to make 13 ?)
(w-8)(w-5)=0
w-8=0
w=8
w-5=0
w=5
we are right back where we started from !!!
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