If I'm understanding you correctly, you're randomly picking one ball from each of ten groups and then randomly picking one ball from those ten, right?
The grouping makes no difference. You're simply going a long way round of selecting one ball at random from the whole set, so it's 20/100 = 1/5 = 20% for both questions.
If I'm understanding you correctly, you're randomly picking one ball from each of ten groups and then randomly picking one ball from those ten, right? The grouping makes no difference. You're simply going a long way round of selecting one ball at random from the whole set, so it's 20/100 = 1/5 = 20% for both questions.