Mathematics · May / June 2024 · Paper 21 · Question 22
0580
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Bag A and bag B each contain red counters and blue counters only. Stephan picks a counter at random from bag A and Jen picks a counter at random from bag B. The probability that Stephan picks a red counter is 0.4 . The probability that Stephan and Jen both pick a red counter is 0.25 . Find the probability that Stephan and Jen both pick a blue counter. [4]
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0.225 oe [4]
M3 for 0.25 × ( ) 1 – 1 – 0.4 oe 0.4 OR
M2 for 0.25 0.4
or M1 for 0.4 × p = 0.25 oe
M1 for (1 –theirP(Jen red))×(1 – 0.4) oe
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