Mathematics · Oct / Nov 2025 · Paper 21 · Question 20
0580
As printed in the paper
The question as text
Bag A Bag B Bag A contains 5 white balls and 3 black balls. Bag B contains 3 white balls and 1 black ball.
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20(a)[1]
0 [1]
20(b)(i)[2]
[2]
B1 for 3 8 or for 3 and 1 correctly placed on the 4 4 same pair of branches
20(b)(ii)[3]
18 oe 32 [3]
M2 for 5 3 3 1 × their + their × their oe 8 4 8 4
or M1 for one correct branch e.g. 5 3 3 1 × × their or their their oe 8 4 8 4
20(c)[3]
11 40 oe [3]
M2 for 5 1 3 2 × + × oe 8 5 8 5
or M1 for one product of the form 5 k 3 k oe (k = 1, 2, 3 or 4) × × or 8 5 8 5
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