Tree Diagrams: Eduqas GCSE Higher November 2019 Paper 1 Q15

Higher November 2019 Paper 1 Q15

EduqasHigherCurrent spec6 marksTree Diagrams

15. Vera has a pot containing 4 red grapes and 6 green grapes.
She takes a grape at random and eats it.
She then takes another grape at random and eats it.

(a) Complete the probability tree to show this information. [3]

Probability tree: 1st Grape branches Red and Green; each followed by 2nd Grape branches Red and Green; all six probabilities left blank

(b) Work out the probability that the second grape Vera eats is green. [3]

Completed tree: first grape R 4/10, G 6/10; after R: R 3/9, G 6/9; after G: R 4/9, G 5/9 — Mark scheme (a)

Scheme	Marks	Comments
Correct tree diagram	B3	B1 for left hand branches correct B1 for top right branches correct B1 for bottom right branches correct Allow equivalent fractions or exact decimals in all cases. If no marks then SC1 for two correct probabilities

Mark scheme (b)

Scheme	Marks	Comments
\(\dfrac{4}{10} \times \dfrac{6}{9} + \dfrac{6}{10} \times \dfrac{5}{9}\) oe	M2	FT ‘their probability tree’ M1 for either product
\(\dfrac{54}{90}\) oe; ISW	A1	CAO; Ignore any attempts to cancel or decimalise after a correct answer seen \(\dfrac{54}{90}\) implies 3 marks but an answer of \(\dfrac{6}{10}\) or \(\dfrac{3}{5}\) without working earns 3 marks only if a correct tree seen in part (a).
	(6)