Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A spinner has equal sectors numbered to . Find the probability that the arrow stops on (a) a prime number, (b) a number greater than .
For balls, discs or spinners with equally likely outcomes, . To find an unknown number of balls, write the probability with the unknown and solve the equation. An event and its complement add up to .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Primes. : sectors, so .
Step 2. Greater than . : sectors, so .
Answer: (a) , (b) .
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