# By what percentage will the area of a rectangle increase if its length is increased by 20% and its width by 10%.

To solve this problem, recall the formula for the area of a rectangle. The area of the rectangle is equal to the product of the length and the width. S = a * b, where a is the length and b is the width. To find the percentage of the number, you need to multiply this number by the percentage and divide by one hundred. Let’s increase the length by 20%.

a + 0.2a = 1.2a.

Let’s increase the width by 10%.

b + 0.1b = 1.1b.

Let’s calculate the area.

S = 1.1b * 1.2a = 1.32ab.

Let’s calculate by what percentage the area has increased. To find how many percent one number is from another, you need to find the quotient of these numbers, and then translate it into percentages (for this, multiply the resulting number by 100%).

1.2ab – ab = 0.2ab.

0.2ab / ab * 100 = 20%.

Answer: 20%.