Statistics & Probability
Simple Probability (Using a Spinner)
Probability = (number of favorable outcomes) / (total number of outcomes). It is always between 0 and 1. A spinner with equal sections makes a great model.
Watch & Learn
Watch a clear, friendly video explanation of Simple Probability (Using a Spinner):
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Worked Examples
Follow along with these step-by-step examples. Take your time — there's no rush!
Problem
A spinner has 8 equal sections: 3 red, 2 blue, 3 green. What is P(red)?
Step-by-Step Solution
Favorable outcomes (red): 3
Total outcomes: 8
P(red) = 3/8
Answer
P(red) = 3/8 = 0.375
Problem
Using the same spinner, what is P(not green)?
Step-by-Step Solution
Green sections: 3. Not green: 8 − 3 = 5.
P(not green) = 5/8
Answer
P(not green) = 5/8
Problem
A spinner has 10 equal sections numbered 1–10. What is P(even number)?
Step-by-Step Solution
Even numbers 1–10: 2, 4, 6, 8, 10 → 5 favorable outcomes.
Total: 10
P(even) = 5/10 = 1/2
Answer
P(even) = 1/2
Problem
A bag has 3 red, 4 blue, and 5 green marbles. What is P(blue)?
Step-by-Step Solution
Favorable outcomes (blue): 4
Total outcomes: 3 + 4 + 5 = 12
P(blue) = 4/12 = 1/3
Answer
P(blue) = 1/3
Problem
A spinner has 6 equal sections. What is P(landing on any section)?
Step-by-Step Solution
Every spin must land on one of the 6 sections.
P(any section) = 6/6 = 1
A probability of 1 means the event is certain.
Answer
P = 1 (certain event)
Your Turn — Practice Problems
Try all 5 problems on your own first. Write out your work — that's how it sticks!
💡 Tip: Don't peek at the answers until you've genuinely tried each one.
Spinner: 4 red, 6 blue (10 total). P(blue)?
Spinner: 5 equal sections (1–5). P(3)?
Spinner: 8 sections, 2 yellow. P(yellow)?
Spinner: 6 sections, 4 red. P(not red)?
Spinner: 12 sections, 3 purple. P(purple)?
Bag: 5 red, 5 blue. P(red)?
Spinner: 10 sections, 7 green. P(not green)?
A die has 6 sides. P(rolling a 5)?
Bag: 3 red, 3 blue, 4 green. P(green)?
Spinner: 4 equal sections. P(any one section)?
A die has 6 sides. P(rolling an even number)?
Bag: 2 yellow, 8 white. P(not yellow)?
Finished all 12? Give yourself a pat on the back — then check your work!
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