Whole numbers less than 20 are 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. How to know if they are divisible by 3? Add the numbers, and if the sum is divisible by 3.
A proportion is the name we give to a statement in which 2 ratios are equal. Proportions are built off of ratios. It is usually written in one of 2 ways
"The mean is the average of the numbers: a calculated "central" value of a set of numbers. To calculate it: add up all the numbers, then divide by how many numbers there are." -- Math is Fun
