# The perimeter of the polygon ABCDE is 75 cm. Find the DE side if AB = BC = 12 cm, the CD side is 5 cm

August 28, 2021 | education

| **The perimeter of the polygon ABCDE is 75 cm. Find the DE side if AB = BC = 12 cm, the CD side is 5 cm larger than the AB side, and the AE side is 2 cm smaller than the CD side.**

1. Let us calculate what is the side CD of the polygon, if it is known that it is 5 cm larger than the side AB. And AB = 12 cm.

12 + 5 = 17 cm.

2. Next, we find what the side AE is equal to, if it is known that it is 2 cm less than the side CD.

17 – 2 = 15 cm.

3. Now let’s find what the side DE is equal to, if it is known that the perimeter of the given polygon is 75 cm. The perimeter is the sum of the lengths of all sides of the polygon.

75 – 12 – 12 – 17 – 15 = 19 cm.

Answer: In a given polygon, the DE side is 19 cm.

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