To the best of your ability estimate:
1. How much older was Hashirama than Tobirama?
2. How old was Hashirama when he died?
3. How old was Tobirama when he died?
4. How old was Hiruzen when he became hokage?
5. How old was Hiruzen when he became sensei of Jiraiya Oro and tsunade?
6. How old was Hiruzen during the 1st, 2nd and 3rd ninja war?
7. Minato during the 3rd war?
8. Minato when he became hokage?
By my own estimations....
1. Not by much. They don't look very different as kids in terms of age, so...I'm betting one or two years.
2. No way to accurately know, but I'm guessing he was in his early thirties, just based on circumstance.
3. Late, maybe mid, thirties, I guess. Again, hard to say.
4. He didn't look much older than part 2 Naruto...seventeen, I say.
5. Well, all three Sanin graduated at age six according to the wiki, which takes this info from databooks, so seeing as Hiruzen is around eighteen/nineteen years older than them...I have to say he became their sensei at twenty four or twenty five.
6. Well, the first is obviously in his teens, and if we guess that the Sanin were in their twenties during the second war, he'd be in his forties. Based on Minato's age in relation to his, the third war must have happened during his early to mid fifties.
7. Based on the next answer, I'd have to guess he's twenty one or twenty two, maybe a bit younger. He doesn't look that far off from The Last Naruto in terms of age.
8. I think it has been confirmed Minato died when he was twenty four, so I'm gonna say that, as his reign only lasted for couple months, I recall.