Finding the unknown (mult/div)

Lesson

Practice

Lesson

Finding the missing number in multiplication questions

We have seen how to find the missing number when our number problem involves addition or subtraction, but what if our number problem includes multiplication or division? We can still use some of those strategies, but there are other strategies that may fit the problem we are working on, such as:

multiplication facts, or times tables,
multiplying by multiples of ten, or
turnarounds.

In Video 1, we look at how some of these strategies can help us find missing values in multiplication problems.

What about division?

Since division is closely related to multiplication, we can use some of the same strategies that we used with multiplication. In particular, fact families are one of the best strategies for working with division. How can they help? Well, let's work through some examples in Video 2, to find the missing number in our division problems.

Remember!

There are other ways to find missing numbers, so you may have ideas of your own to use as well.

Examples

Question 1

What must $j$j be equal to so that $6\times j=30$6×j=30 is true?

QUESTION 2

What must $p$p be equal to so that $6\div p=3$6÷p=3 is true?

QUESTION 3

What must $t$t be equal to so that $t\times6=12\times4$t×6=12×4 is true?

Outcomes

6.PA2.01

Demonstrate an understanding of different ways in which variables are used (e.g., variable as an unknown quantity; variable as a changing quantity)

6.PA2.04

Determine the solution to a simple equation with one variable, through investigation using a variety of tools and strategies (e.g., modelling with concrete materials, using guess and check with and without the aid of a calculator)