4. A rectangle with area 1,600 m2 is 4 times as long as it is wide. What is the sum of the diagonals?

We need to write out algebraic equations to describe the information we have, then solve them using substitution.

We will define length as a and width as b.

we know that a x b = 1600 cm3  (area = length x width)

and a=4b

So, we can substitute the vaule 4b for a in the first equation:

4b x b = 1600  

we can simplify to 4b2 = 1600

divide both sides by 4:

b2 = 400

take the square root of each side:

b = √400

b=20

So we know the width = 20

length = 4  x width = 80

5+2x=a

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