Difficulty: Easy
Correct Answer: 1687401
Explanation:
Introduction / Context:
Squaring a near-1000 or near-1300 number can be made efficient with a near-base approach. Here, 1299 is one less than 1300, so the binomial (a − b)^2 expansion is especially convenient and reduces risk of arithmetic errors.
Given Data / Assumptions:
Concept / Approach:
Let 1299 = 1300 − 1. Then (1300 − 1)^2 = 1300^2 − 2*1300*1 + 1^2. This avoids full long multiplication while remaining exact and transparent.
Step-by-Step Solution:
1) 1300^2 = 1,690,000.2) 2*1300*1 = 2600; subtract: 1,690,000 − 2,600 = 1,687,400.3) Add 1^2 = 1 → 1,687,401.4) Therefore, 1299^2 = 1,687,401.
Verification / Alternative check:
Check last two digits: 99 × 99 ends with 01, matching the result's ending 01. The magnitude also aligns with being slightly less than 1300^2 (1,690,000), confirming plausibility.
Why Other Options Are Wrong:
1684701 and 1685401 are off by hundreds or thousands due to middle-term mistakes; 1692601 exceeds 1300^2; 1585301 is far too small, indicating a base or place-value error.
Common Pitfalls:
Forgetting to subtract 2ab; misplacing zeros in 1300^2; arithmetic slips when subtracting 2600 from 1,690,000.
Final Answer:
1687401
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