4400 Higher November 2008 Paper 3 Q15
15 There are 9 counters in a bag.
7 of the counters are red and 2 of the counters are white.
Ajit takes at random two counters from the bag without replacement.
(a) Calculate the probability that the two counters are red. (2)
(b) Calculate the probability that the two counters have different colours. (3)
| Scheme | Marks |
|---|---|
| \(\frac{7}{9} \times \frac{6}{8}\) | M1 |
| \(\frac{42}{72}\) oe | A1 |
| (2) |
Notes
A1: for \(\frac{42}{72}\) oe inc \(\frac{7}{12}\)
| Scheme | Marks |
|---|---|
| \(\frac{7}{9} \times \frac{2}{8} + \frac{2}{9} \times \frac{7}{8}\) | M1 |
| M1 | |
| \(\frac{28}{72}\) oe | A1 |
| (3) | |
| (5 marks) |
Notes
M1: for one of correct products \(\frac{7}{9} \times \frac{2}{8}\) or \(\frac{2}{9} \times \frac{7}{8}\)
or M2 for \(1 - (a) - \frac{2}{9} \times \frac{1}{8}\)
M1: for sum of both correct products
A1: for \(\frac{28}{72}\) oe inc \(\frac{7}{18}\)
SC
M1 for \(\frac{7}{9} \times \frac{2}{9}\) or \(\frac{2}{9} \times \frac{7}{9}\)
M1 for \(\frac{7}{9} \times \frac{2}{9} + \frac{2}{9} \times \frac{7}{9}\)