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GATE CS 2020 · General Aptitude

Question 7

MCQPrinted as GA Q.72 marksWrong answer: −2/3Easy (estimate)

Question

If P=3P = 3, R=27R = 27, T=243T = 243, then Q+S=Q + S =

Choose one option
Official answer and solution
Official answer
C
From
Official GATE 2020 answer key

Solution

Identify the underlying geometric progression across the letter series P, Q, R, S, T.

The letters P, Q, R, S, T represent consecutive terms in an alphabetical sequence. We are given P=3P = 3, R=27R = 27, and T=243T = 243.

Notice that P=31P = 3^1, R=33=27R = 3^3 = 27, and T=35=243T = 3^5 = 243. This is a geometric sequence where the common ratio between consecutive terms is 3:

  • P=31=3P = 3^1 = 3
  • Q=32=9Q = 3^2 = 9
  • R=33=27R = 3^3 = 27
  • S=34=81S = 3^4 = 81
  • T=35=243T = 3^5 = 243

We need to find Q+SQ + S:

Q+S=9+81=90.Q + S = 9 + 81 = 90.
Final answer

C

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

Source

Paper
GATE 2020 Computer Science and Information Technology (CS)
Question
7 of 65, printed as GA Q.7
Section
General Aptitude

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