Question

The solution of the following by using suitable identities:
$109\times 108$ is ------

Answer 1

The given product $109\times 108$ can be rewritten as $(100+9)\times (100+8)$ and we solve it as follows:

$(100+9)(100+8)=100(100+8)+9(100+8)=(100\times 100)+(100\times 8)+(9\times 100)+(9\times 8)=10000+800+900+72=11772$

Hence, $109\times 108=11772$.