Why does my child solve 3x = 12 as x = 36?
Your child multiplies to undo a multiplication, instead of dividing.
Why children do it
3x means 3 times x, and the opposite of multiplying is dividing. Children who see the 3 next to x often multiply by it again, especially if 3x looks like one thing rather than 3 lots of x. 3x = 12 means three of something make 12, so x = 4.
How to help at home
Ask what undoes multiplying. Dividing does: 3x = 12 becomes x = 12 ÷ 3.
The right way
Solve: 3x + 5 = 20
- 3x = 15Subtract 5 from both sides.
- x = 5Divide both sides by 3.
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