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The number line shows 1,300 and the two perfect squares closest to it. What is the least number that must be added to 1,300 to get a perfect square?

Class 8Squares and Square RootsSquares and Roots
  • A4
  • B69
  • C73
  • D37

Step-by-Step Solution

The marked squares are and . 1,300 is past 1296, so the next square is 1369: .
Answer: B) 69

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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