O-LevelMathematicsProbability4024/12 · Oct/Nov 2017 · Q193 Marks
Each time an archer fires an arrow, the probability that she hits the target is 0.7 . She fires two arrows.
- (a)Complete the tree diagram.[1]
- (b)(i)Find the probability that (i) she hits the target twice,[1]
- (b)(ii)(ii) she hits the target exactly once.[1]
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 2017). The mark or mark type is shown in brackets.
- [1] 19(a) Probabilities 0.7 and 0.3 on the correct branches
- [1] 19(b)(i) 0.49 oe
- [1] 19(b)(ii) 0.42 oe
- FT from their diagram, provided their diagram probabilities are less than 1, and 0 < ans. < 1.
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