Question

What is the square of the number $89$ using direct multiplication method?

Answer 1

WE need to find square of $89$

Thus ${89}^2=(80+9{)}^2$

By using $(a+b{)}^2=a(a+b)+b(a+b)$
Here $a=80,b=9$
Therefore, ${89}^2=80(80+9)+9(80+9)$
$=$ ${80}^2+720+720+9^2$
$=6400+1440+81$
$=7921$