If Rob flips 3 coins what is the chance that they will come up all tails?

The correct answer was : 1/8 , but it doesn’t make sense to me ! can you explain why it is 1/8 ?

First things first. To find the probability of ONE thing happening, you’ve got to figure out how many times the thing you’re asking about will happen, and put that over how many times anything will happen. Flipping a coin is pretty easy. It could come up heads, or it could come up tails. There are two possibilities, and one chance that it’ll come up tails one out of two.

Probability of tails on one coin flip = 1/2

That’s the total number of possibilities it’ll come up tails over the total number of possibilities, altogether. Got it?

Now, you’ve got to figure out, separately, the probability that it’ll come up tails EACH of the three times. That’s simple. They’re all the same. The chance is 1/2 that it’ll come up tails each time you flip the coin. So you got three 1-in-2 chances.

First try: 1/2

Second try: 1/2

Third try: 1/2

How do you figure out what the odds are of it coming up tails all three times? Multiply! Remember, to multiply fractions, multiply all the top numbers to get the top number and multiply all the bottom numbers to get the bottom number:

1/2 × 1/2 × 1/2 = 1/8

There’s 1/8 chance of it coming up tails three times in a row.

For more information about the GED test and GED test preparation, visit the GED Academy at http://www.passGED.com

There’s a few ways to write a probability. Let’s take a dice. Odds of rolling any number on a dice, let’s say 3, is 1 in 6. You can say “1 in 6″ or “1:6″ or “1/6.” They all mean the same thing. Out of 6 rolls of a die, odds are you’ll get a 3 one time. Pretty simple, right?

Let’s take it a step further. You got 2 dice. What’s the odds you’ll get 2 threes on one roll? The way you figure it out is multiplying the odds of each: 1/6 x 1/6 = 1/36. You’ve got one-in-thirty-six odds of rolling 2 threes.

But what are your odds of rolling a total of 6? There are five possible dice combinations that will give you a total of 6:

1 and 5

5 and 1

2 and 4

4 and 2

3 and 3

So, what are the odds of rolling a total of 6 on two dice?

1) 5/12

2) 3/36

3) 5/36

4) 1/6

5) 1/12

What’d'ya think? It’s pretty straightforward. There are 36 possible combinations, total, when rolling two six-sided dice. That’s why you got a 1 in 36 odds of rolling 2 threes. So, if there’s 5 possible combinations to get a total of 6, that’s 5 possibilities out of 36. The odds are 5/36. Not great!

Probability is pretty easy once you get the hang of it… and I bet you’ll see it on the test!

Good luck with that GED!

For more information about the GED test and GED test preparation, visit The GED Academy at http://www.passGED.com.