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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Math Antics | Math Video Lessons for Free plus more

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Grade 7 " The Number System | Common Core State Standards Initiative

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CCSS.Math.Content.7.NS.A.1.b Understand p + q as the number located a distance |q| from p, in the positive or negative direction depending on whether q is positive or negative. Show that a number and its opposite have a sum of 0 (are additive inverses). Interpret sums of rational numbers by describing real-world contexts.

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A Rational Number can be made by dividing two integers.
(An integer is a number with no fractional part.)

Example:

1.5 is a rational number because 1.5 = 3/2 (3 and 2 are both integers)

Most numbers we use in everyday life are Rational Numbers.

Here are some more examples:

Oops! The square root of 2 cannot be written as a simple fraction! And there are many more such numbers, and because they are not rational they are called Irrational.

Another famous irrational number is :

Formal Definition of Rational Number

More formally we say:
A rational number is a number that can be in the form p/q
wherep and q are integers and q is not equal to zero.
So, a rational number can be:

Where q is not zero

Examples:

Just remember: q can't be zero

Using Rational Numbers

Fun Facts ....

The ancient greek mathematician Pythagoras believed that all numbers were rational, but one of his students Hippasus proved (using geometry, it is thought) that you could not write the square root of 2 as a fraction, and so it was irrational.

But followers of Pythagoras could not accept the existence of irrational numbers, and it is said that Hippasus was drowned at sea as a punishment from the gods!

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A Rational Number can be made by dividing two integers. (An integer is a number with no fractional part.) 1.5 is a rational number because 1.5 = 3/2 (3 and 2 are both integers) Most numbers we use in everyday life are Rational Numbers. Here are some more examples: Oops!

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A video lesson on rational numbers: what are they, what aren't they, how do you add, subtract multiply and divide them