From a rectangle the length of the sides of which is 5 cm and 3 cm, a strip with sides of 3 cm

From a rectangle the length of the sides of which is 5 cm and 3 cm, a strip with sides of 3 cm and 1 cm was cut off. Find the area of the remaining part?

Model a rectangle (with side lengths of 5 cells and 3 cells), select a rectangle on it (with side lengths of 1 cell and 3 cells), shade the rest of it.

1 way.

Let’s find the area of the larger rectangle: 5 * 3 = 15 cm2.
Find the area of the smaller rectangle: 1 * 3 = 3 cm2.
Let’s find the area of the middle rectangle: 15 – 3 = 12 cm2.

Method 2.

Let’s find the length of the middle (required) rectangle: 5 – 1 = 4 cm.
Let’s find the area of the middle (required) rectangle: 4 * 3 = 12 cm2.
Answer: the rest of the area is 12 cm2.