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Date November 2017 Marks available 3 Reference code 17N.1.SL.TZ0.S_1
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Complete Question number S_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.

N17/5/MATME/SP1/ENG/TZ0/01.a

[3]
a.

Find the probability that exactly one of the selected balls is green.

[3]
b.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

correct probabilities

N17/5/MATME/SP1/ENG/TZ0/01.a/M     A1A1A1     N3

 

Note:     Award A1 for each correct bold answer.

 

[3 marks]

a.

multiplying along branches     (M1)

eg 5 8 × 3 7 ,   3 8 × 5 7 ,   15 56

adding probabilities of correct mutually exclusive paths     (A1)

eg 5 8 × 3 7 + 3 8 × 5 7 ,   15 56 + 15 56

30 56   ( = 15 28 )     A1     N2

[3 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 4—Statistics and probability » SL 4.5—Probability concepts, expected numbers
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Topic 4—Statistics and probability » SL 4.6—Combined, mutually exclusive, conditional, independence, prob diagrams
Topic 4—Statistics and probability

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