GRE study exam guide has following
If an integer is randomly selected from all positive 2-digit integers, what is the probability that the integer chosen has at least one 4 in the tens place or the units place?
I understand probability of being in 10s place is $1/9$ and the probability of being in the units place is $1/10$
When I add $1/9$ + $1/10$ the answer is $19/90$. However, answer says $1/5$.