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Counting and Basic Probability · Question 34 of 65

Question 34

EasyOriginal question

A raffle has tickets numbered 1 to 30, and one ticket is drawn at random. What is the probability that the number on it is a prime number?

Options for question 34

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. Primes up to 30: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, which is 10 numbers.

  2. Probability =1030=13= \frac{10}{30} = \frac{1}{3}.

Worth noting

Forgetting that 2 is prime gives 930=310\frac{9}{30} = \frac{3}{10}; counting 1 as prime gives 1130\frac{11}{30}. 23\frac{2}{3} is the chance of NOT a prime.

Concept
Listing favourable outcomes carefully
Typical time
40 s
Your time
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The rule this testsBasic probability
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