Question

If the digit $1$ is placed after a $2$-digit number whose tens is $t$ and one’s digit is $u$, the new number is ______.

Answer 1

Find the unknown number.

Given: A $2$-digit number whose tens is $t$ and one’s digit is $u$.

Therefore, the number is $10t+u$.

$1$ is placed after $2$-digit number .

Placing $1$ after the two-digit number is the indication that, shifts the given digit towards the left, so that $t$ is now a hundred’s digit and $u$ is now a tens digit.

Hence the number is $100t+10u+1$.