Share both sides

Forty-five chairs from the store are set in five equal rows. How many chairs are in one row?

Five equal rows as an equation

One row holds 9 chairs.

Call that number x. Five rows hold 5x chairs, where 5x means 5 times x. That is 45, so 5x = 45.

Adding or taking away does not help here. The chairs in one row, x, were multiplied by 5. To undo a multiplication, share. Sharing is the same as dividing.

Share both sides by 5. On the left, 5x shared by 5 is x. On the right, 45 ÷ 5 = 9. So x = 9.

Rule: Multiplying and sharing undo each other. Multiply or share both sides by the same number, not 0.

A crate of mangoes is divided into four equal heaps. One heap holds six. Let x be the mangoes in the crate, so x ÷ 4 = 6. The crate was shared, so undo the sharing by multiplying. Multiply both sides by 4. On the left, x ÷ 4 × 4 is x. On the right, 6 × 4 = 24. So x = 24.

Try the lab to finish this lesson.