JAMB Mathematics 2021 Objective — Question 18

Question 18 of 40 from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2021 Objective paper, with the correct answer and a full explanation.

18. Two numbers are selected at random from the numbers 2,4,5. Find the probability that the sum of the two is odd (a) 1/2 (b) 1/6 (c) 5/6 (d) 2/3

A. 1/2
B. 1/6
C. 5/6
D. 2/3Correct

Explanation

Out of the six possible ordered ways of selecting two numbers from {2,4,5}, four give an odd sum (2+5, 5+2, 4+5, 5+4) and two give an even sum (2+4, 4+2). So P(odd sum) = 4/6 = 2/3.

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