The two sides of a parallelogram are 3: 4, and its perimeter is 70.

Find the sides of the parallelogram. The perimeter is the sum of the lengths of the sides. We write down the solution.
Let’s denote one part by x, then one side is 3x, the other side is 4x. We get the following expression.
P = (a + b) × 2.
70 = (3x + 4x) × 2.
2 × 7’s = 70.
14 x = 70.
x = 70 ÷ 14 = 5.
Find one side of the parallelepiped.
3x = 3 × 5 = 15 cm.
4x = 4 × 5 = 20 cm.
This means that one side is 15 cm, and the other side is 20 cm.