Multiple choice

What approximate value should come in place of question mark (?) in the following questions? $( (12.05)^2 - (8.99)^2 + (13.99)^2 - (17.08)^2 = ? )$

  1. -20

  2. -40

  3. -30

  4. -50

  5. -10
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Use difference of squares formula: a² - b² = (a+b)(a-b). Round the values: (12.05)² - (8.99)² ≈ (12+9)(12-9) = 21 × 3 = 63. For the second pair: (13.99)² - (17.08)² ≈ (14-17)(14+17) = (-3) × 31 = -93. Total: 63 - 93 = -30. Option C is correct. The key insight is recognizing the difference of squares pattern rather than calculating each square individually.

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