(197 × 203) = ?

We can write following problem such as,


(197 × 203) = (200 – 3)(200 + 3)


From the formula, (a +b)(a – b) = a2 – b2


We get,


(200 – 3)(200 + 3) = 2002 – 32 = 40000 – 9 = 39991.

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