Question

Solve mentally$.$

$1,00,000-78,342$

Answer 1

Given numerical expression is $1,00,000-78,342$

Replace every zero from the left with $9$ and the last zero with a $10$

$$\begin{gathered} 100000 \\ \underbrace{|}\underbrace{|}\underbrace{|}\underbrace{|}\underbrace{|} \\ 999910 \end{gathered}$$

Now subtract each digit from $9$ and last digit from $10$

$$\begin{gathered} 999910 \\ -78342 \\ \overline{21658} \end{gathered}$$

Hence$,$ the value of $1,00,000-78,342$ is $21658$