NUMBAT OER - Open Educational Resources

3. Multiplying and dividing

The last equation in the previous section ended up as:

3x = 18

The expression 3x represents the value of x multiplied by three. The aim of the exercise is to find the value of x. Again, we need to transform both sides of the equation so that we are left with the unknown on one side of the equation. Here, we divide both sides by 3:

3x/3 = 18/3
x = 18/3 = 6

The short cut method is simply to move the multiplier to the other side of the equals sign, and turn it into a divisor, thus:

3x = 18
x = 18/3
x = 6

Click to view an animated example.

Similarly, a divisor becomes a multiplier when it is moved across to the other side of the equation:

x/7 = 5
x = 7 × 5 = 35

Click to view an animated example.