The sides of the rectangle are 12cm and 8cm. How will the perimeter of the rectangle change if its length is increased by 3cm.

Given:
length – 12 cm;
length2 – more by 3 cm;
width – 8 cm;
width2 – 8 cm;
perimeter -? cm.
perimeter2 -? cm.
The task of calculating the sum of the lengths of the sides of a rectangle. The perimeter of the rectangle is calculated by the formula: P = 2 * (a + b) – where, a is the length, b is the width.
1) P1 = 2 * (a + b) = 2 * (12 + 8) = 2 * 20 = 40 (cm);
Let’s calculate the width of the second rectangle:
2) 12 + 3 = 15 (cm);
3) P2 = 2 * (a + b) = 2 * (15 + 8) = 2 * 23 = 46 (cm);
4) 46 – 40 = 6 (cm).
Answer: the perimeter of the rectangle will change by 6 cm if its length is increased by 3 cm.