Probability question?

I think you need some very general help on the basics.

An "event" is some particular outcome of a spin. It could be "it comes up 10" or "it comes up red" or "it comes up between 5 and 12". Those are all possible events. But those are make up of the most basic events, that it comes up as one of 22 different numbers, 0, 00 or 1 to 22.

If all the basic events have the same probability (getting a 5 has same probability of getting a 00, e.g.), Then all you have to do is this:

1. Find how many of the basic events make up the defined event? Call that A.

2. Find out how many basic events there are in total. Call that B.

The answer: the probability of the event happening is A/B.

You want to know the probability that the number comes up 16 or greater. There are 7 possible numbers, 16 17 18 19 20 21 22. The 0 and 00 don't enter into it.

There are 22 possible numbers, so the probability is 7/22.

Just about every probability problem is done like that. Here's another example: You pick a card from a standard deck of playing cards. What's the probability that it's a face card or a red 4? Well, each suit has 3 face cards: J Q K. That's 12. There are 2 red 4's: Hearts and Diamonds. So that's 14 cards total. The probability is 14/52, since there are 52 cards in the deck.

These problems involve nothing more than counting and then taking the ratio. These are very basic probability problems.

When you count up the "basic" events in a more complex one, be careful to look at how the descriptions overlap. Using your roulette wheel, suppose you wanted to know the probability that the number is less than 10, or odd.

There are 9 numbers less than 10.

There are 11 odd numbers.

9 + 11 = 20, but that's too large.

There are 5 numbers that are BOTH less than 10 and odd (1 3 5 7 9), so you have to subtract that since otherwise you've counted them twice.

There are 9 + 11 - 5 = 15 that satisfy. So 15/24 is the answer.

Note that there are 24-15 = 9 numbers that DON'T satisfy the conditions:

0 00 10 12 14 16 18 20 22.

There is a basic rule of probability that the probability of all the (mutually exclusive) events have to add up to 1. So you can often do problems by looking at the opposite result. E.g., you spin your wheel 10 times. What's the probability of getting at least one 00? Well, the even of getting at least one is the opposite of getting none. Since the probability of NOT getting 00 on a roll is 23/24, The probability of not getting 00 on 10 rolls is (23/24)^10 -- since each roll is independent, you can multiply the probability on each rolls. So the probability of getting at least one 00 is 1 minus the probability getting none = 1 + (23/24)^10.

Sorry for the long-winded answer. It's just that it looks like you need to review all the basics of what's going on.

There are 7 spins that are 16 or greater {16, 17, 18, 19, 20, 21, 22}

There are 24 possible outcomes (0, 00, 1, 2, 3, ..., 19, 20, 21, 22}

Divide to get the probability of the given event.

P(spin ≥ 16) = 7/24