- 1981709
- 1951609
- 2031719
- 1951719
- 2011609
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Answer: B official key
Approach: Square near a round number: (a − b)² = a² − 2ab + b².
Solution:
1397² = (1400 − 3)²
= 1400² − 2 × 1400 × 3 + 3²
= 1,960,000 − 8,400 + 9
= 1,951,609.
Cetking shortcut: Last digit 7² → 9 and last two digits 97² → 09 kill C and D; size ≈ 1.95 million kills A and E.
Answer: B

