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