Higher June 2019 Paper 5 Q6

OCRHigherCurrent spec4 marksTree Diagrams

6 A bag contains 4 red counters and 3 blue counters only.
Jack picks a counter at random and then replaces it.
Jack then picks a second counter at random.

(a) Complete the tree diagram.

Tree diagram: first pick Red with probability 4/7 and Blue blank; second pick after Red: Red 4/7, Blue blank; after Blue: Red blank, Blue blank

[2]

(b) Work out the probability that Jack picks two red counters. [2]

Mark scheme (a)

Answer	Marks	Part marks and guidance
\(\frac{3}{7}\), \(\frac{3}{7}\), \(\frac{4}{7}\), \(\frac{3}{7}\) correctly placed	2	M1 for 2 or 3 probabilities correctly placed	Accept equivalent fractions, decimals or %s (3 figures needed for dec or %)