(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.