Idea 5of 22Builds onEvery section goes on the bottom
Split unequal sections into equal parts
How do you find a probability when sections differ in size?
Today you'll discover
- why you cannot just count sections
- how to split them
- how to write the fraction
Think firstThree sections, all different sizes
What is the probability of landing on green?
Decide first, then press Next. Make every part the same size before you count.
A spinner with an orange third, a blue half and a green sixth. The three sections are numbered 1 to 3; then dashed lines split them into 6 equal parts, numbered 1 to 6; then green 1/6 is written beside it. The last step shows a spinner that is half blue and a quarter each orange and green.
See the whole ideathe big idea and the key word, in one place
The big idea
When sections differ in size, split them into equal parts, then count the parts.
A third and two thirdsOrange covers a third, blue two thirds: split blue in two. 3 equal parts, so orange is 1/3 and blue 2/3.
Easy to get wrongThree sections does not mean thirds. Each probability is 1/3 only when the three sections are the same size.
Key word
- equal parts
- pieces of the same size, so each one is equally likely
Ready to use it?
- Find a probability on a spinner with sections of different sizes.