Why does my child think √9 + √16 = √25?
Your child adds under the root, such as √9 + √16 as √25 = 5 instead of 3 + 4 = 7.
Why children do it
It looks like the rule for multiplying roots, √a × √b = √(ab), which children have just learnt. But adding doesn't work that way: √9 + √16 is 3 + 4 = 7, while √25 is 5. Working out each root on its own first shows the difference.
How to help at home
Ask them to work out each root on its own first, then add: √9 + √16 is 3 + 4.
The right way
Work out: √9 + √16
- 3 + 4Work out each root first: √9 = 3 and √16 = 4.
- 7So √9 + √16 = 7, not √25 = 5.
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