The length of the rectangle is 4 cm. What should be its width so that the perimeter of the rectangle is less than 20?

The perimeter of a rectangle is the sum of its two sides of length and two sides of its width.

Let’s compose an inequality in which we denote the width of the rectangle by x.

x + x + 4 + 4 <20.

2 x + 8 <20.

Next, in place of the x, we substitute the value, starting with one:

2 * 1 + 8 = 10

10 <20 means that a width of 1 cm is suitable for us.

Next, in place of x, substitute the number 2.

2 * 2 + 8 = 4 + 8 = 12.

12 <20 is also suitable.

Now let’s substitute the number 3.

2 * 3 + 8 = 6 + 8 = 14.

14 <20 – come up.

Number 4.

4 * 2 + 8 = 16.

Number 5.

5 * 2 + 8 = 10 + 8 = 18.

Number 6.

6 * 2 + 8 = 12 + 8 = 20 – not suitable.

This means that the width is from 1 to 5 cm.