I’m a math moron and could use some help.

Let’s say that on a roll of a 10-sided die a 7 or higher is considered a “success.” That means on each die roll there’s a 40% chance of getting a success (4/10).

Let’s say now that you’re rolling a batch of three 10-sided dice. How would you calculate the chances of getting either exactly no successes, exactly one success, exactly two successes, or exactly three successes?

Hit the spoiler for my failed attempt to do it:

[spoiler]Chances of getting no successes:

6/10 * 6/10 * 6/10 = .216 or ~21%

Chances of getting one success:

4/10 * 6/10 * 6/10 = .144 or ~14%

Chances of getting two successes:

4/10 * 4/10 * 6/10 = .096 or ~9%

Chances of getting three successes:

4/10 * 4/10 * 4/10 = .064 or ~6%

These should be the only four outcomes (no successes, one success, two successes, three successes) but their combined percent chances don’t add up to anywhere near 100%.[/spoiler]

Help would be appreciated. And no, it’s not for homework.