In order to find the sides of a parallelogram, we will recall the properties of the sides of a parallelogram and the formula for finding the perimeter of a parallelogram.
So, from the condition it is known that one of the sides of the parallelogram is 3 cm, and its perimeter is 20 cm.
Opposite sides of a parallelogram are equal to each other. That is, the length of one pair of sides is known to us as 3 cm.
Let’s denote by x cm the length of the second side.
P = 2 (a + b);
2 (3 + x) = 20;
3 + x = 20: 2;
3 + x = 10;
x = 10 – 3;
x = 7 cm is the length of the second pair of sides of the parallelogram.
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