| Date | November 2017 | Marks available | 3 | Reference code | 17N.1.sl.TZ0.1 |
| Level | SL only | Paper | 1 | Time zone | TZ0 |
| Command term | Find | Question number | 1 | Adapted from | N/A |
Question
A bag contains 5 green balls and 3 white balls. Two balls are selected at random without replacement.
Complete the following tree diagram.
[3]
a.
Find the probability that exactly one of the selected balls is green.
[3]
b.
Markscheme
correct probabilities
A1A1A1 N3
Note: Award A1 for each correct bold answer.
[3 marks]
a.
multiplying along branches (M1)
eg\(\,\,\,\,\,\)\(\frac{5}{8} \times \frac{3}{7},{\text{ }}\frac{3}{8} \times \frac{5}{7},{\text{ }}\frac{{15}}{{56}}\)
adding probabilities of correct mutually exclusive paths (A1)
eg\(\,\,\,\,\,\)\(\frac{5}{8} \times \frac{3}{7} + \frac{3}{8} \times \frac{5}{7},{\text{ }}\frac{{15}}{{56}} + \frac{{15}}{{56}}\)
\(\frac{{30}}{{56}}{\text{ }}\left( { = \frac{{15}}{{28}}} \right)\) A1 N2
[3 marks]
b.
Examiners report
[N/A]
a.
[N/A]
b.
Syllabus sections
Topic 5 - Statistics and probability » 5.5 » The probability of an event \(A\) is \(P\left( A \right) = \frac{{n\left( A \right)}}{{n\left( U \right)}}\) .
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