CAT (QA) PYQs

How many three-digit numbers are greater than $100$ and increase by $198$ when the three digits are arranged in the reverse order?

The sum of all the digits of the number $(10^{50}+10^{25}-123)$, is

The number of integers $x$ such that $0.25 < 2^x < 200$, and $2^x + 2$ is perfectly divisible by either $3$ or $4$, is