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