O-LevelMathematicsProbability4024/12 · Oct/Nov 2014 · Q214 Marks
A bag contains 5 balls, 2 of which are blue and 3 are red. One ball is taken, at random, from the bag. If it is red it is put back into the bag. If it is blue it is not put back into the bag. A second ball is taken, at random, from the bag. Part of the tree diagram that represents these outcomes is drawn below. [Figure 21.1]
- (a)Complete the tree diagram.[1]
- (b)(i)both balls taken are blue,[1]
- (b)(ii)the second ball taken is blue.[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 2014). The mark or mark type is shown in brackets.
- [1] (a) Correct completion of tree diagram
- [1] (b) (i) 1/10
- [2] (ii) 17/50 or ft from their tree diagram
- [2] M1 for [ (2/5 × 1/4) or their(b)(i) ] + [ (3/5 × 2/5) ]
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