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GATE CS 2018 · General Aptitude

Question 5

MCQPrinted as GA Q.51 markWrong answer: −1/3Easy (estimate)

Question

What is the missing number in the following sequence?

2, 12, 60, 240, 720, 1440, _____, 0

Choose one option
Official answer and solution
Official answer
B
From
Official GATE 2018 answer key

Solution

Identify the pattern of successive multipliers connecting adjacent terms.

Compute the ratios between consecutive terms:

  • 12/2=612 / 2 = 6
  • 60/12=560 / 12 = 5
  • 240/60=4240 / 60 = 4
  • 720/240=3720 / 240 = 3
  • 1440/720=21440 / 720 = 2

The multipliers decrease by 1 at each step: 6,5,4,3,2,…6, 5, 4, 3, 2, \dots
Therefore, the next multiplier must be 1:

Missing term=1440×1=1440\text{Missing term} = 1440 \times 1 = 1440

Following this, the subsequent multiplier is 0:

1440×0=01440 \times 0 = 0

which matches the final term in the sequence.

Final answer

B

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper
GATE 2018 Computer Science and Information Technology (CS)
Question
5 of 65, printed as GA Q.5
Section
General Aptitude

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