Times tables

Groups of the same size

20 minutes

Start the lesson

Before you read anything

Four small piles, six stones in each. Make them. Do not count the lot yet.

Say out loud how many piles there are, and how many are in one pile. Two numbers, and they are not the same kind of thing.

The question module 3 left you with

Module 3 kept saying forty is four tens. That is a count of equal groups, said out loud, before anybody called it one.

Every count of equal groups is a multiplication. Four tens, four sixes, four of anything — as long as the piles match.

What you just did

Four baskets with six in each, counted six, twelve, eighteen, twenty-four, and then written once as four times six.

The two numbers do different jobs

:x nutshell-equal-groups

Piles that all hold the same amount. If one pile is short, counting them as a multiplication gives the wrong answer.


In $4 \times 6$ the first number says how many piles and the second says how many in each. :Equal groups is the whole condition — nothing else is needed, and nothing less will do.

Not four and six

Musa

read $4 \times 6$ and wrote 10

Nakato

counted her piles and wrote 24

Musa added the labels instead of the stones. Four and six describe the piles. Neither of them is an amount of anything.

The bar you already have

Module 1 cut a bar into two parts. This is that bar with four parts and every one the same length — which is exactly why one number is enough to say how big they are.

Check yourself

Six to try

Each one gives you the number of groups and the size of one. Say both out loud before you answer.

1

$3$ groups of $4$. How many altogether?

2

$9$ groups of $7$. How many altogether?

3

Otim puts $5$ bricks in each of $9$ rows. How many bricks is that?

4

$4 \times 6$

5

$4 \times 3$

6

$5$ groups of $7$. How many altogether?

Away from the screen

Groups, rows and boxes Read it here, or print it and work on paper.
Groups, rows and boxes, page 1 Groups, rows and boxes, page 2

Open the PDF Save it to print

Show that you have it

The box, with one side missing

You are told the total and how many groups. The size of one group is the thing nobody has told you.

1

$4 \times \square = 16$. What goes in the box?

2

$4 \times \square = 48$. What goes in the box?