SSC CGL Tier 1

Missing Number

Missing Number is a topic where a figure (usually a triangle, circle, square or wheel) is given with numbers arranged around it and one number is missing. You have to find the pattern connecting the numbers and find the missing one.

 

 

Basic Concept:

 

In missing number questions, numbers are placed in a specific arrangement - like corners of a triangle, sections of a circle or spokes of a wheel. There is always a mathematical relationship between these numbers. Your job is to find that relationship and apply it to find the missing number.

 

Types of Missing Number Questions in SSC CGL:

 

Type 1 - Triangle Based Numbers are placed at the corners and center of a triangle.

 

Example:

        6
       / \
      /   \
     8-----4
        ?  (center)

 

Logic: Center = Sum of corners / 3 = (6+8+4)/3 = 18/3 = 6

Or sometimes: Center = Product of two corners - third corner

Always check what operation connects the given numbers to find the pattern.

 

 

Type 2 - Circle Based A circle is divided into sections and numbers are placed in each section.

 

Example: Circle divided into 4 sections: Top=3, Right=7, Bottom=5, Left=?

 

Correct Logic: Opposite sections add up to the same number.

 

  • Top and Bottom are opposite: 3 + 5 = 8
  • Left and Right are opposite: ? + 7 = 8
  • So ? = 8 - 7 = 1

 

Answer: 1

 

 

Type 3 - Wheel Based Numbers are placed at the ends of spokes of a wheel. Opposite spokes always add up to the same value.

 

Example: 

Wheel with 6 spokes: Top=3, Top-right=9, Bottom-right=5, Bottom=7, Bottom-left=11, Top-left=?

 

Logic: Opposite spokes add to same value.

  • Top + Bottom = 3 + 7 = 10
  • Top-right + Bottom-left = 9 + 11 = 20... not matching

 

Let me use a correct clean example:

 

Wheel with 6 spokes: Top=4, Top-right=8, Bottom-right=6, Bottom=6, Bottom-left=2, Top-left=?

  • Top + Bottom = 4 + 6 = 10
  • Top-right + Bottom-left = 8 + 2 = 10 ✅
  • Top-left + Bottom-right = ? + 6 = 10
  • So ? = 4

 

Answer: 4

 

 

Type 4 - Grid or Matrix Based Numbers in rows and columns follow a pattern.

 

Example:

| 2 | 4 | 8  |
| 3 | 6 | 12 |
| 4 | 8 | ?  |

 

Logic: Third number = Second number × 2

  • 4×2=8
  • 6×2=12
  • 8×2=16

Answer: 16

 

Common Patterns Used in Missing Number Questions:

 

  • Opposite sections/spokes add up to the same value
  • Sum of all numbers in one set = constant
  • Center = sum of surrounding numbers / count
  • Numbers follow multiplication pattern
  • Numbers follow addition or subtraction pattern
  • Numbers follow square or cube pattern
  • Clockwise or anti-clockwise increasing series

 

How to Solve Missing Number Questions:

 

Step 1 - Look at all complete sets of numbers (without missing value). 

Step 2 - In circle/wheel: check if opposite pairs add to same value first. 

Step 3 - In triangle: check if center = sum of corners divided by number of corners. 

Step 4 - If these do not work, try multiplication or subtraction. 

Step 5 - Apply the confirmed pattern to find the missing number. 

Step 6 - Always verify your answer using all complete sets.

 

Quick Tricks:

 

Trick 1 - In circle questions: opposite sections always add to the same value. This is the most reliable pattern.

Trick 2 - In triangle questions: center = (sum of all corners) / 3 is the most common pattern.

Trick 3 - In wheel questions: opposite spokes add to the same value - same as circle logic.

Trick 4 - In grid questions: check each row separately first to find the operation.

Trick 5 - Always verify with ALL complete sets before finalizing the answer.

 

Important Tips:

 

  • Never guess - always verify the pattern with complete sets first
  • If a pattern works for some sets but not others - it is wrong, find another pattern
  • Opposite pairs logic (circle and wheel) is the most frequently tested pattern in SSC CGL
  • 2 to 3 questions come from this topic every year
  • With practice each question takes only 30 seconds
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