Question

Calculate the square value of $421$ using direct multiplication method.

Answer 1

We can write ${421}^2=(400+21{)}^2$

Using $(a+b{)}^2=a(a+b)+(a+b)$
Here $a=400,b=21$
Therefore, ${421}^2=400(400+21)+21(400+21)$
$=$ ${400}^2+8400+8400+{21}^2$
$=160000+16800+441$
$=177241$