Question

Squares of which of the following numbers will have 1(one) at their unit's place :

• A. 57
• B. 81
• C. 139
• D. 73
• E. 64
• F. 831

Answer 1

Answer: (B), (C), (F)

139
831
81

Let's check each of the options one by one.
(A) 57
Unit place is 7. Its square is 49. Therefore 9 will be present at the unit place of square of 57.
(B) 81
Unit place is 1. Its square is 1. Therefore 1 will be present at the unit place of square of 81.
(C) 139
Unit place is 9. Its square is 81. Therefore 1 will be present at the unit place of square of 139.
(D) 73
Unit place is 3. Its square is 9. Therefore 9 will be present at the unit place of square of 73.
(E) 64
Unit place is 4. Its square is 16. Therefore 6 will be present at the unit place of square of 64.
(F) 831
Unit place is 1. Its square is 1. Therefore 1 will be present at the unit place of square of 831.