# What Exactly IS a Number? | An Introduction

Hi, and welcome this video lesson on numbers. All kinds of numbers are important when learning math including integers, decimals, fractions, percentages, etc.

Let’s go ahead and review what some of these terms mean, so that we can do better next time. An integer is a positive whole number, negative whole number, or zero; for example, 8 is an integer, so is negative 9. 1/2 is not and neither is negative point 4.

A percentage is part per hundred; for example, 20 percent is 20 parts per hundred, or point 20. The best way to think of percentages is to think of a pie. 100 percent of a pie is 1 whole pie. 50 percent of a pie is half a pie. Make sense?

A fraction is an expression where one number is being divided by another number; for example, 10 divided by 20 is a fraction, but don’t forget, sometimes fractions can be simplified.

For example, 10/20, you can divide both top and bottom numbers by 10 and have 1 over 2, or 1/2, which is much easier to think about.

All rational numbers can be written as a positive or negative whole number, or zero, being divided by another positive or negative whole number.

This is pretty all-encompassing; it includes fractions, negatives, positives, zero, everything.

For example, negative 5 is a rational number, but so is negative point 5. Make sense?

A decimal contains a whole number or zero and a portion of the whole number which is to the right of the decimal point; for example, 20 point 53 is a number in decimal form, 20 to the left of the decimal and 53 to the right.

All rational numbers are either terminating numbers, where the numbers to the right of the decimal end, or repeating numbers, where the numbers the right of the decimal continue for infinity.

An example of a repeating decimal would be the number point 3333333… for infinity. Let’s make sure we can identify, in order, every one of these types of numbers.

Place these in order from least to greatest: 12^{2}, 12 percent, 1 point 2 and 12. Looks like the first number is going to be 12 percent because 12 out of 100 is point 12.

Then, we’re going to have 1 point 2, then we’ll have 12, and finally we have 12^{2}, which is actually 144. I hope that helps. Thanks so much for watching, and until next time, happy studying!