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GATE CS 2026 Set 2 · General Aptitude

Question 7

MCQ2 marksWrong answer: −2/3Medium (estimate)

Question

Two tiles are missing in Panel I. Which one of the options in Panel II is the appropriate choice for the missing tiles?

Panel I: a 3 by 3 arrangement of tiles, each a 3 by 3 grid of filled and open dots; the middle-right and bottom-right tiles are missing (marked ?). Panel II: four candidate pairs of stacked tiles (i), (ii), (iii) and (iv), each showing its own pattern of filled and open dots.
Choose one option
Official answer and solution
Official answer
A
From
Official GATE 2026 answer key

Solution

Count the number of filled black circles in each tile of the 3 by 3 grid in Panel I and observe the magic-square sum.

Counting the filled black circles in each tile of Panel I gives:

  • Row 1: 8,1,68, 1, 6 (sum =15= 15)
  • Column 1: 8,3,48, 3, 4 (sum =15= 15)
  • Column 2: 1,5,91, 5, 9 (sum =15= 15)

This is the standard 3×33 \times 3 magic square where every row, column, and diagonal sums to 1515. Therefore:

  • Row 2, Column 3 needs 15−(3+5)=715 - (3 + 5) = 7 filled black circles.
  • Row 3, Column 3 needs 15−(4+9)=215 - (4 + 9) = 2 filled black circles (which also satisfies Column 3: 6+7+2=156 + 7 + 2 = 15).

In Panel II, option (i) has 77 filled circles in the top tile and 22 filled circles in the bottom tile.

Final answer

Option (A)

Common trap

Miscounting the top tile of (ii) which has 6 filled dots instead of 7.

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

Source

Paper
GATE 2026 Computer Science and Information Technology - Session 2 (CS2)
Question
7 of 65
Section
General Aptitude

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