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Date May Specimen paper Marks available 3 Reference code SPM.2.SL.TZ0.4
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number 4 Adapted from N/A

Question

A six-sided biased die is weighted in such a way that the probability of obtaining a “six” is 7 10 .

The die is tossed five times. Find the probability of obtaining at most three “sixes”.

[3]
a.

The die is tossed five times. Find the probability of obtaining the third “six” on the fifth toss.

[3]
b.

Markscheme

recognition of binomial      (M1)

X ~ B(5, 0.7)

attempt to find P (X ≤ 3)       M1

= 0.472 (= 0.47178)        A1

[3 marks]

a.

recognition of 2 sixes in 4 tosses    (M1)

P (3rd six on the 5th toss)  = [ ( 4 2 ) × ( 0.7 ) 2 × ( 0.3 ) 2 ] × 0.7 ( = 0.2646 × 0.7 )         A1

= 0.185 (= 0.18522)       A1

[3 marks]

b.

Examiners report

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

Syllabus sections

Topic 4—Statistics and probability » SL 4.8—Binomial distribution
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Topic 4—Statistics and probability

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