Planning & Decision Making · Guided Practice

Calculating Basic Probabilities

8 questions with answers. Try each one before revealing the answer.

1
A bag contains 6\displaystyle 6 red counters, 4\displaystyle 4 blue counters and 5\displaystyle 5 green counters.
One counter is chosen at random.
Calculate the probability that it is blue.
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2
A bag contains 6\displaystyle 6 red counters, 4\displaystyle 4 blue counters and 5\displaystyle 5 green counters.
One counter is chosen at random.
Calculate the probability that it is not blue.
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3
In a class of 25\displaystyle 25 pupils, 14\displaystyle 14 cycle to school.
One pupil is chosen at random.
Calculate the probability that the pupil does not cycle to school.
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4
A fair six-sided die is rolled once.
State whether 'rolling a 3\displaystyle 3' and 'rolling an even number' are mutually exclusive. Justify your answer.
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5
Two counters are taken from a bag, one after the other, and the first is not replaced.
State whether the two events are independent or dependent. Justify your answer.
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6
A fair coin is flipped and a fair die is rolled.
State whether 'the coin lands on heads' and 'the die shows a 6\displaystyle 6' are independent. Justify your answer.
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7
A student flips a fair coin and it lands on heads 5\displaystyle 5 times in a row.
The student says the next flip is more likely to be tails because tails is overdue.
Name the fallacy the student is using and explain why the student is wrong.
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8
A spinner has 8\displaystyle 8 equal sections numbered 1\displaystyle 1 to 8\displaystyle 8.
Calculate the probability of spinning a number less than 3\displaystyle 3 or a number greater than 6\displaystyle 6.
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