Squares and square roots
INTRODUCTION
•Numbers like ,1,4,9,16,25 are known as square
numbers
•If a natural number m can be expressed as n2 where n
is also a natural number, then m is a square number.
If a number to be square has 1 or 9 in the
units place then its square ends in 1.
 When square number ends in 6 the
number whose square it is will have either
4 or 6 in its units place.

 Any natural number n and (n+ 1), then
(n+1)2 – n2 = (n2 + 2n +1)- n2 = 2n +1
 There are 2n non perfect square numbers
between the squares of the numbers n and
(n+1).
 Sum of the first n odd natural numbers is
n2 .
 If a natural number cannot be expressed
as a sum of successive odd numbers
starting with 1, then it is not a perfect
square.
 12 = 1
112 = 121
1112 = 123321
11112 = 12344321
111112 = 123454321
1111112 = 1234554321
11111112 = 12345654321
 72
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
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= 49
672
=4489
6672
=444889
66672
=44448889
666672 =4444488889
6666672 =444444888889
 We can find out the square of a number
without having two multiply the numbers.
For e.g. 232 = (20 +3)2 =20(20+3)+3(20+3)
= 202 + 20*3 + 3*20 + 32
 For any natural number m > 1, we have
(2m)2 + (m2 – 1) = (m2 + 1)2 .
In mathematics, a square root of a number a is a
number y such that y2= a, or, in other words, a
number y whose square (the result of multiplying
the number by itself, or y × y) is a. For example,
2
4 and -4 are square roots of 16 because 4 = (4)2 = 16.
 In Ancient India, the knowledge of theoretical and
applied aspects of square and square root was at least as
old as the Sulba Sutras, dated around 800–500 BC
(possibly much earlier). A method for finding very good
approximations to the square roots of 2 and 3 are given
in the Baudhayana Sulba Sutra. Aryabhata in
the Aryabhatiya (section 2.4), has given a method for
finding the square root of numbers having many digits.
 Finding square roots through repeated
subtraction
81−1=80
80 − 3=77
77 − 5=72
72 − 7=65
65 − 9=56
56 − 11=45
45 − 13=32
32− 15=17
17 − 17=0
From 81 we have subtracted successive odd
numbers starting from 1 and obtained 0 at 9th
step. √81 = 9
 Finding square root through prime
factorization
Each prime factor in a prime factorization of the
square of a number, occurs twice the number
of times it occurs in the prime factorization of
a given square number, say 324.
324=2*2*3*3*3*3
By pairing the prime factors, we get
324=2*2*3*3*3*3=22 * 32 * 32 = (2*3*3)2
So,
2  3  3  18
1. There are 500 children in a school. For a P.T. drill they have to stand in
such a manner that the numbers of rows is equal to number of columns.
How many children would be left out in this arrangement?
2. Find the smallest square that is divisible by each of the numbers 4,9 and
10?
3. Find the square root of 2.56?
4. Find the square root of 4489?
5. Find the square root of 100 and 169 by repeated subtraction?
6. Find the square of 71?