Kenny has a box of 5 kittens.
If Kenny reaches into the box without looking, what's the chance that he gets a white kitten?
We can't say for sure. We need to make a prediction.
A prediction is a guess about what could happen.
We can use probabilities to make a prediction.
Probability is the likelihood that an outcome will happen out of all the possible outcomes.
To find a probability, we divide the number of favorable, or desired, outcomes by the total possible outcomes.
Tip: "P" often stands for probability.
A favorable outcome is the outcome we want to get.
Let’s make a prediction about which cat Kenny gets using probability. 😀
First, we count all the possible outcomes.
There are 5 kittens. There are 5 possible outcomes.
Next, we list the number of favorable outcomes.
We want Kenny to get a white kitten.
2 kittens are white. There are 2 favorable outcomes.
We divide the favorable outcomes by the total possible outcomes to get the probability:
The probability of getting a white kitten is 2/5. This is also equal to 4/10, or 0.4, or 40%. ✅
Sally is playing with this shape spinner game.
Let’s say she spins it 8 times.
How many times can she expect to get a square?
To figure this out, first let's find the probability of getting a square for each spin.
There are 4 squares in the spinner. This is the number of favorable outcomes.
There are 8 total possible outcomes.
Do you remember how to find probability?
Yes! Divide the number of favorable outcomes by the total possible outcomes.
The probability of getting a square for every spin is 4/8.
Now, we multiply this probability by the number of times she spins.
How many times does she spin?
Yes, 8 times.
We can simplify 32 / 8:
32 ÷ 8 = 4
The best prediction is that she will get a square 4 out of 8 spins.
This is her called her expected value.
Fantastic job.
Now, start the practice to help you learn more.