Handling Data 7
2 marks · HardA bag contains 5 red counters and 3 blue counters. Two counters are taken from the bag one after the other, without replacement. What is the probability that both counters are red? Give your answer as a fraction in its simplest form.
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Also accept: 5/14
Common mistakes: \frac{5}{16}; \frac{25}{56}; \frac{3}{14}
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Marking points
M1 · 1 mark · Correct method for probability with no replacement: or working shown for multi-stage selection.
A1 · 1 mark · Correct final answer: , simplified fraction. (follow-through)
Worked solution
Probability first counter is red: . After removing 1 red, 4 red and 3 blue remain: probability second is red: . Multiply: . Simplify: .