Test: Squares And Square Roots- 1 - UPSC MCQ

The answer is 1681 because it is the only number which has it's last digit as a number which a perfect square can have . 9×9=81 the last digit is 1.

Option B is correct because the unit digit of 161 is 1 and if unit digit of any digit ends with 1 the its square will also end with 1.

Option 1:
√576 = 24

Option 2:
√841 = 29

Option 3:
√778 = 27.89 It is not perfect square

Option D:
√529 = 23

Hence, the answer is option C.

Since, 1 x 1 = 1

         2 x 2 = 4

         3 x 3 = 9

         4 x 4 = 16

         5 x 5 = 25

         6 x 6 = 36

         7 x 7 = 49

Thus, 36 is a perfact square number between 30 and 40.

√0.053361
= √(5.3361 × 10^(-2))
= √(5.3361) × √(10^(-2))
= ±2.31 × 0.1
= ±0.231

12² = 12*12 = 144

13² = 13*13 = 169

Now numbers are between144 and 169 are:

145, 146, 147,.............168

Total number = 24

So total numbers lies between 144 and 169 is 24

When squaring the number 5278, the unit digit is determined by the square of the unit digit of the original number.

Since the unit digit of 5278 is 8, squaring it gives 8 × 8 = 64.

Therefore, the unit place digit of 5278² is 4.
Therefore correct answer : Option A