A Perfect Square Always Ends in 0,1,4,5,6,9 as Last Digit
The following...
Question
The following numbers are obviously not perfect squares. Give reason. (i) 1057 (ii) 23453 (iii) 7928 (iv) 222222 (v) 64000 (vi) 89722 (vii) 222000 (viii) 505050
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Solution
We know that, numbers having 2,3,7or8 at units place are not perfect squares.
That is because:
12=1
22=4
32=9
42=16
52=25
62=36
72=49
82=64
92=81
Also,
102=100
1002=10000
Hence, any perfect square will end with 1,4,5,6,9 or even number of zeros.
All the given numbers end with either 2,3,7,8 or with odd number of zeros.