alleryWhich of these cannot possibly be the LAST digit (units digit) of a perfect square?
A1
B4
C7
D9
Answer & Solution
Correct answer: C. 7
By checking units digits of n² for n = 0,1,2,…,9: possible last digits of a perfect square are {0,1,4,5,6,9}.
So 2, 3, 7 and 8 can NEVER be the units digit of a perfect square.
**Option C (7) is therefore correct.**
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