38 NUMBERS •^ SQUARE ROOTS
A square root is a number that you multiply by itself
once to get a particular square number. The symbol
we use for the square root is √.
Square roots
Find the roots
Use the table on this page to work out the
answers to these questions.
10 is the square root of which number?
4 is the square root of which number?
TRY IT OUT
Squares and square roots are opposites
- so if 25 is the square of 5, then 5 is the
square root of 25. The word we use in maths
for this is “inverse”.
We can use this squares table to find square
roots. Let’s look at the square number 64. To
find its square root, follow its row and column back
to the start. We find 8 at the start of 64’s row and
column, so we know 8 is the square root of 64.
Let’s look at 36. Its square root is 6, the
number that we multiply by itself, or square,
to get 36. We write it like this: √36 = 6
We square
5 to get
25
5 is the
square root
of 25
The square
numbers are
in dark purple
Follow the row or
column back to find
the square root
because
6 × 6 = 36 or 62 = 36
Square roots are the
opposite, or inverse, of
square numbers.
1×
11
22
33
44
55
66
77
88
99
1010
1111
1212
2
2
4
6
8
10
12
14
16
18
20
22
24
3
3
6
9
12
15
18
21
24
27
30
33
36
4
4
8
12
16
20
24
28
32
36
40
44
48
5
5
10
15
20
25
30
35
40
45
50
55
60
6
6
12
18
24
30
36
42
48
54
60
66
72
7
7
14
21
28
35
42
49
56
63
70
77
84
8
8
16
24
32
40
48
56
64
72
80
88
96
9
9
18
27
36
45
54
63
72
81
90
99
108
10
10
20
30
40
50
60
70
80
90
100
110
120
11
11
22
33
44
55
66
77
88
99
110
121
132
12
12
24
36
48
60
72
84
96
108
120
132
144
What is the square root of 81?
Square
5 25
Answers on page 319
√ 36 = 6
(^) Sq
uare root
038_039_Square_roots_cube.indd 38 29/02/2016 14:09