ECZ 2018 · GCE Paper 2 · Question 5 — Probability

A box contains 20 black, 12 red and 4 white buttons. Two buttons are picked at random one after another without replacement. Pseudo code given: Start; Enter a, r, n; R = 1 - r; If R = 0 THEN print 'the value of r is not valid' Else Sn = a1 - r^nR; End if; Print Sn; Stop.

(a(i)) Draw a tree diagram to show all the possible outcomes.[3]

Verified working — step 1

Total buttons = 20+12+4 = 36.

(a(ii)) What is the probability that both buttons are white?[2]

Verified working — step 1

P(W,W) = (436) x (335)

(b) Construct a flow chart corresponding to the pseudo code.[5]

Verified working — step 1

Flow chart:

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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