Question
Evaluate the following using identities:
$991 \times 1009$
$991 \times 1009$
✓
Answer
We have,
$991 \times 1009$
$= (1000 - 9)(1000 + 9)$
$= (1000)^2 - (9) [(a + b)(a - b) = a^2 - b^2]$
$= 1000000 - 81 [Where a = 1000 and b = 9]$
$= 999919$
Therefore, $991 \times 1009 = 999919$
$991 \times 1009$
$= (1000 - 9)(1000 + 9)$
$= (1000)^2 - (9) [(a + b)(a - b) = a^2 - b^2]$
$= 1000000 - 81 [Where a = 1000 and b = 9]$
$= 999919$
Therefore, $991 \times 1009 = 999919$
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