Handling Data 2
2 marks · NormalA bag contains 2 red balls and 3 blue balls. One ball is chosen at random, replaced, and another is chosen.
What is the probability that both balls are red?
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4/25 (±0.01)
Also accept: 0.16; 4/25; 0.16 (2 d.p.)
Common mistakes: Using combinations, not product rule
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Marking points
M1 · 1 mark · Identifies probability for one red ball: 2/5
A1 · 1 mark · Correctly squares to get (2/5) × (2/5) = 4/25 or 0.16
Worked solution
Probability red on first pick: 2/5
Probability on second pick (after replacing): 2/5
Probability both red: 2/5 × 2/5 = 4/25 = 0.16