General Mathematics Paper 2, May/June. 2010
 Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 Main
Weakness/Remedies
Strength

Question 5

Two fair dice are thrown.
M is the event described by "the sum of the scores is 10" and
N is the event described by "the difference between the scores is 3".
(a) Write out the elements of M and N.
(b) Find the probability of M or N.
(c) Are M and N mutually exclusive? Give reasons.

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Observation

This question was reported to be popular and well attempted by majority of the candidates. However, a few of them did not list the elements of M and N as required but drew the sample space when 2 dice are thrown. Some of them who listed these elements did not do so completely. Majority of them were reported not to be able to state correctly the condition for which events are mutually exclusive. Candidates were expected to show that M = { (4,6) , (5,5), (6,4}. N = { (1,4), (2,5), (3,6), (4,1),
(5,2), (6,3) }. Probability of M = 3/36 = 1/12. Probability of N = 6/36 = 1/6.
Probability of Nor M:1/12 + 1/6 = 1/4. M and N are mutually exclusive because no element is  common to both sets. Thus the two events cannot happen at the same time i.e. n(M n N) = O. It was also reported that while listing the elements of N, some candidates would list (1,4) but not (4,1).