A number that is multiplied by itself to form a product is called a square root of that product. The operations of squaring and finding a square root are inverse operations.
By definition Ö25 is the number you would multiply times itself to get 25 for an answer. Because we are familiar with multiplication, we know that Ö25 = 5 . Numbers like 25, which have whole numbers for their square roots, are called perfect squares
You need to memorize at least the first 15 perfect squares
Perfect square
A perfect square is a number whose positive square root is a whole number.
Square root
1
Ö1 = 1
4
Ö4 = 2
9
Ö9 = 3
16
Ö16 = 4
25
Ö25 = 5
36
Ö36 = 6
49
Ö49 = 7
64
Ö64 = 8
81
Ö81 = 9
100
Ö100 = 10
121
Ö121 = 11
144
Ö144 = 12
169
Ö169 = 13
196
Ö196 = 14
225
Ö225 = 15