Handling Data 5
2 marks · NormalA box contains 7 blue pens and 5 red pens. A pen is selected at random. It is replaced, and then another pen is selected at random. Find the probability of selecting a blue pen both times.
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49/144 (±0.01)
Also accept: 0.340 (3 sf)
Common mistakes: Multiplying by 7/12 then by 6/11 (without replacement)
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Marking points
M1 · 1 mark · Identifies probability of blue pen on one selection as 7/12 and multiplies correct probabilities for both selections.
A1 · 1 mark · Gives final answer 49/144 or correctly rounded decimal equivalent.
Worked solution
Probability of picking a blue pen on one selection:
As the pen is replaced, the events are independent.
Final answer: 49/144