Answer
$0.1$
Work Step by Step
We know that probability$=\frac{\text{number of favorable outcomes}}{\text{number of all outcomes}}.$
We have $\frac{100}{5}=20$ numbers in total. (Because every fifth number satisfies the criteria.) So the total number of outcomes is $20$.
There are $1+1=2$ numbers that we are looking for (one of them is the number $30$ and the other one is the number $100$). So the number of favorable outcomes is $2$.
Thus, we have the probability:
$P=\frac{2}{20}=0.1$
