What is a ratio?

Hello, and welcome to Myriora Maths! Here's a necklace with red beads and blue beads. For every three red beads, there are two blue beads. We say the ratio of red to blue is three to two. Let's see what that means.

Look at the pattern: red, red, red, blue, blue. Then it repeats. In every group of five beads, three are red and two are blue. We write the ratio with two dots: three to two.

The order matters. Red to blue is three to two. But blue to red is two to three.

Make the necklace longer. Two groups have six red and four blue. Three groups have nine red and six blue. The ratio is still three to two, because the pattern hasn't changed.

A ratio can give us fractions too. Each group has five beads, and three of them are red. So three fifths of the beads are red, and two fifths are blue.

Let's try one together. A pattern has one star for every four moons. What is the ratio of stars to moons? Say it out loud!

One star for every four moons: the ratio is one to four!

Here's a question that catches lots of people. A necklace has three red beads for every two blue beads. What fraction of the beads are red? Some people say three over two. But a fraction is out of the whole group, and each group has five beads. So three fifths are red!

Your turn! There are four cats and six dogs. What is the ratio of dogs to cats? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! The question says dogs first, so the ratio is six to four!

Quick review. A ratio compares two amounts, like three red for every two blue. We write it with two dots: three to two. The order matters. And the ratio stays the same when the pattern repeats. See you next time!