A Square Root is the opposite or inverse of squaring a number. The square root of a number is the value that when multiplied by itself gives the number.
The symbol for the square root is √
To write the square root of nine, we would write √9
3 x 3 = 9 - so √9 is 3
In Key Stage 2, we only need to deal with square roots of perfect squares and mainly only up to 100 (10²) which is why remembering all the square numbers up to 100 is worthwhile, after all they are part of the times tables so it should be easy!
The first 10 square numbers are: 1, 4, 9, 16, 25, 36, 49, 64, 81 and 100,
so if asked
"What is the square root of forty nine?"
we can see that it is seven, because .... 7 x 7 = 49 ..... √49 = 7
"What is the square root of one hundred?"
it is ten, because .... 10 x 10 = 100 ..... √100 = 10
At Key Stage 2, it is just a case of 'trial and error' - seeing which number when multiplied by itself gives the correct answer.
Your child needs to know that the square root of a number is the inverse of squaring, and if they remember the square numbers up to 10, they should be able to answer any question on square roots.