What is the length of the second side in a rectangle, given that the sum of the 2 opposite sides is 14 cm and the area of the rectangle is 21 cm²?
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What is the length of the second side in a rectangle, given that the sum of the 2 opposite sides is 14 cm and the area of the rectangle is 21 cm²?
As we know that the two opposite sides of the rectangle add up to 14 and that, in a rectangle, each pair of opposite sides are equal, we can calculate the size of each one as follows:
We will call the other two opposite sides and calculate the unknown variable as follows:
We will then divide both sides by 7 to get:
3
Look at the rectangle ABCD below.
Side AB is 6 cm long and side BC is 4 cm long.
What is the area of the rectangle?
Since opposite sides are equal in a rectangle, if two opposite sides sum to 14, each of those sides must be cm long.
It doesn't matter! The problem asks for the length of the second side. Since we found one pair of sides is 7 cm, the other pair must be 3 cm.
Yes! Let one side be . Then: , which gives . But the direct method shown is simpler!
Rectangle problems can have decimal dimensions! Always check your work by verifying both the area and the given side relationship.
If the second side were 7 cm, we'd have a square with area cm², not 21 cm² as required.
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