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Official PYQ · 2026

GATE CS 2026 Set 1 Q10 — General Aptitude

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An unbiased six-faced dice whose faces are marked with numbers 1,2,3,4,51,2,3,4,5, and 66 is rolled twice in succession and the number on the top face is recorded each time. The probability that the number appearing in the second roll is an integer multiple of the number appearing in the first roll is ____\_\_\_\_

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Answer: C

Let the outcome of the first roll be xx and the second roll be yy, where x,y∈{1,2,3,4,5,6}x, y \in \{1, 2, 3, 4, 5, 6\}.

Since the dice is rolled twice, the total number of possible outcomes in the sample space is:

∣S∣=6×6=36|S| = 6 \times 6 = 36

We need to find the probability that yy is an integer multiple of xx (i.e., y=k⋅xy = k \cdot x for some positive integer kk). Let's list the favorable outcomes (x,y)(x, y) systematically for each possible value of xx:

  • If x=1x = 1: yy can be any multiple of 11, which are {1,2,3,4,5,6}\{1, 2, 3, 4, 5, 6\} →\rightarrow 66 outcomes
  • If x=2x = 2: yy can be {2,4,6}\{2, 4, 6\} →\rightarrow 33 outcomes
  • If x=3x = 3: yy can be {3,6}\{3, 6\} →\rightarrow 22 outcomes
  • If x=4x = 4: yy can be {4}\{4\} →\rightarrow 11 outcome
  • If x=5x = 5: yy can be {5}\{5\} →\rightarrow 11 outcome
  • If x=6x = 6: yy can be {6}\{6\} →\rightarrow 11 outcome

Summing these up, the total number of favorable outcomes is:

N=6+3+2+1+1+1=14N = 6 + 3 + 2 + 1 + 1 + 1 = 14

Therefore, the required probability is:

P=1436=718P = \frac{14}{36} = \frac{7}{18}

Thus, the correct option is C.

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