Multiplication meaning and facts (grade 3) · lesson

Equal groups

and

Tap each one to count it

💡 Multiply when you have equal groups: the number of groups times the number in each group.

When every group has the same number, you can multiply instead of counting one by one.

In 3 × 6, the first number tells how many groups. The second tells how many are in each group.

Adding more is not the same. Getting 4 more is adding. Giving some away is taking away. Only equal groups is multiplying.

Some stories have groups inside groups, like boxes of bags. Find how many are in one big group first. Then multiply again.

🧠 Let's work it out

There are 3 plates. Each plate has 6 cookies. How many cookies?

That is 3 groups of 6, so write 3 × 6.
Count by 6s: 6, 12, 18.
So there are 18 cookies.

What do you think comes next?

multiply: put equal groups together to find the total
product: the answer when you multiply
equal groups: groups that all have the same number

🔗 Intro to multiplication · Khan Academy ↗

Use a fact you know

💡 A hard fact can be built from an easy fact you already know.

You don't have to know every fact by heart. Start from a fact you do know.

To times by 4, you can times by 2 and then double. To times by 8, times by 4 and double again. To times by 9, you can times by 10 and take one group away.

You can also split a fact into two easy ones. 8 × 6 is 8 × 5 plus one more 8: 40 + 8 = 48.

🧠 Let's work it out

Find 9 × 4.

9 × 2 = 18.
4 is double 2, so double 18.
18 + 18 = 36. So 9 × 4 = 36.

What do you think comes next?

double: add a number to itself, or times it by 2

Order does not matter

💡 You can switch the two numbers you multiply and get the same answer.

3 rows of 9 and 9 rows of 3 have the same number of dots. Turn the array on its side and you can see it.

So 3 × 9 and 9 × 3 are both 27. Use the order that is easier for you.

🧠 Let's work it out

Is 2 × 7 the same as 7 × 2?

2 groups of 7 is 14.
7 groups of 2 is 14 too. Yes, they match.

What do you think comes next?

array: things set out in equal rows

Find the missing number

💡 To find a missing number in a times fact, count by the number you know until you reach the total.

In 7 × ? = 35, you know one number and the answer. You need the other number.

Count by 7s and keep track of how many jumps you make. The number of jumps is the missing number.

🧠 Let's work it out

Solve 7 × ? = 35.

Count by 7s: 7, 14, 21, 28, 35.
That is 5 jumps.

What do you think comes next?

factor: one of the numbers you multiply

Break a number apart

💡 Break a big number into tens and ones, multiply each part, then add the parts.

Big facts are easier in pieces. Split the big number into tens and ones.

Times each piece by the small number. Then add the two answers.

🧠 Let's work it out

Find 5 × 13.

Break 13 into 10 + 3.
5 × 10 = 50.
5 × 3 = 15.
50 + 15 = 65.

What do you think comes next?

break apart: split a number into parts that are easy to use