Question

Evaluate the following products without multiplying directly.
$104\times 109$

Answer 1

$104\times 109=(100+4)(100+9)$
Using identity
$(x+a)(x+b)=x^2+(a+b)x+ab,$ we get
$104\times 109$
$=(100{)}^2+(4+9)\times 100+4\times 9$
$=10000+1300+36=11336$