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GATE 2015 CS – Question 5

General Aptitude · Quantitative Aptitude: Probability and Combinatorics · 1 mark · Multiple choice

Given Set $A = \{2, 3, 4, 5\}$ and Set $B = \{11, 12, 13, 14, 15\}$, two numbers are randomly selected, one from each set. What is the probability that the sum of the two numbers equals 16?

  1. 0.20
  2. 0.25
  3. 0.30
  4. 0.33

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Correct answer: (A) 0.20

Explanation

There are $4 \times 5 = 20$ equally likely pairs. The pairs summing to 16 are $(2,14)$, $(3,13)$, $(4,12)$ and $(5,11)$, which is 4 pairs. The probability is $\frac{4}{20} = 0.20$.