How do you find the average of a group of numbers

You add them together and divide it by how many number there are.

Step-by-step explanation:

For example lets say we need to find the average of 12, 15, 18, and 24.

You would do 12+15+18+24

You will get a sum of 69

Then since there are 4 numbers you do 69 divided by 4 and get a quotients of 17.25.

Therefore 17.25 is the average of all four numbers.

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6