O-LevelMathematicsProbability4024/22 · Oct/Nov 2023 · Q56 Marks
A bag contains 40 balls. 28 of the balls are red and the rest are green. Aisha takes a ball from the bag at random, notes its colour and replaces it. Find the probability that this ball is green.
- (a)(i)A bag contains 40 balls. 28 of the balls are red and the rest are green. Aisha takes a ball from the bag at random, notes its colour and replaces it. Find the probability that this ball is green.[1]
- (a)(ii)Aisha repeats this 200 times. Work out the number of times she expects to take a green ball.[1]
- (b)(i)A bag contains 9 blue balls and 7 yellow balls. Sergio takes two balls from the bag at random without replacement. Complete the tree diagram. [Figure Tree Diagram][2]
- (b)(ii)Find the probability that the two balls are the same colour.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [1] 12/40 oe
- [1] FT their 12/40 × 200
- [2] B1 for two or three probabilities correct
- 7/16 on first branch
- 7/15 oe, 9/15 oe, 6/15 oe on second branches
- [2] M1 for one correct product: 9/16 x 8/15 oe or their 7/16 x their 6/15 oe
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