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Between two consecutive perfect squares and there are exactly 44 numbers that are not perfect squares. What is the value of ?

Class 8Squares and Square RootsSquares and Roots
  • A44
  • B23
  • C22
  • D11

Step-by-Step Solution

Between and there are exactly numbers, so gives . Check: and , and 529 − 484 − 1 = 44. The trap 44 simply repeats the count given, 23 is (the next root), and 11 halves 22 one time too many.
Answer: C) 22

Key idea: Properties of perfect squares

Useful patterns to spot a perfect square (and reject non-squares):

- **Last digit**: a perfect square ends in 0, 1, 4, 5, 6, or 9 — NEVER in 2, 3, 7, or 8. So 142 cannot be a perfect square (ends in 2).
- **Number of zeros at the end**: must be even. 100 is a perfect square ; 1000 is not.
- **Squares of even numbers are even; squares of odd numbers are odd.**
- **Sum of consecutive odd numbers**: 1 + 3 + 5 + … + . Try it: .

These let you reject many candidates without doing any heavy work.

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