Equal groups

Hello, and welcome to Myriora Maths! Here are three plates, with four cookies on each plate. How many cookies are there altogether? Let's find a quick way!

Every plate has the same number of cookies: four. These are called equal groups. We could count them all, one by one. Or we can add four, three times: four, eight, twelve. Twelve cookies!

We write it like this. Three, times four, equals twelve. The times sign means groups of. Three groups of four make twelve.

We can also put the cookies in rows. Here are three rows, with four in each row. This is called an array.

Now turn the array round. There are four rows, with three in each row. It's the same dots, so it's the same number: twelve! Three times four is the same as four times three.

Why is multiplying useful? Adding ten fours takes a long time. Ten times four is a quick way to say it: forty. But it only works when every group is the same size!

Let's try one together. Here are five pairs of socks. How many socks are there? Count in twos. Say it out loud!

Two, four, six, eight, ten. Five groups of two make ten. Five times two is ten!

Here's a question that catches lots of people. What is three times four? Some people add instead: three plus four is seven. But three times four means three groups of four. That's four, eight, twelve: twelve!

Your turn! Here is an array, with four rows of five dots. How many dots are there? Pick the right card. You've got fifteen seconds, or pause the video. Go!

Time's up! Count in fives, one row at a time: five, ten, fifteen, twenty. Four rows of five make twenty!

Quick review. Equal groups all have the same number in them. Times means groups of: three times four is three groups of four. And an array shows it in rows, which you can turn round. See you next time!