| Date | May 2013 | Marks available | 3 | Reference code | 13M.1.hl.TZ2.4 |
| Level | HL only | Paper | 1 | Time zone | TZ2 |
| Command term | Draw | Question number | 4 | Adapted from | N/A |
Question
Tim and Caz buy a box of 16 chocolates of which 10 are milk and 6 are dark. Caz randomly takes a chocolate and eats it. Then Tim randomly takes a chocolate and eats it.
Draw a tree diagram representing the possible outcomes, clearly labelling each branch with the correct probability.
Find the probability that Tim and Caz eat the same type of chocolate.
Markscheme
A1A1A1
[3 marks]
Note: Award A1 for the initial level probabilities, A1 for each of the second level branch probabilities.
\(\frac{{10}}{{16}} \times \frac{9}{{15}} + \frac{6}{{16}} \times \frac{5}{{15}}\) (M1)
\( = \frac{{120}}{{240}}{\text{ }}\left( { = \frac{1}{2}} \right)\) A1
[2 marks]
Examiners report
Generally well done. A few candidates didn’t take account of the fact that Caz ate the chocolate, so didn’t replace it. A few candidates made arithmetic errors in calculating the probability.
Generally well done. A few candidates didn’t take account of the fact that Caz ate the chocolate, so didn’t replace it. A few candidates made arithmetic errors in calculating the probability.
