Why this topic matters · 6 min read
Number Analogy is a consistent scorer in SSC CHSL Reasoning. Every year 2-3 questions appear where you must find the relationship between a given pair of numbers and apply the same logic to find the missing number. The questions look simple but have hidden traps. The key skill is spotting the pattern quickly — squares, cubes, differences, products, or mixed operations. With practice you can solve each in under 30 seconds.
What is Number Analogy
In Number Analogy, you are given a pair of numbers that share a specific mathematical relationship. Your job is to find the same relationship in a second pair where one number is missing. Think of it like a lock and key — the first pair shows you which key opens the lock, then you use the same key on the second lock.
- Format: A : B :: C : ? or (A, B) : (C, D) — find the odd one out variant also appears
- The relationship can be addition, subtraction, multiplication, division, squares, cubes, or combinations
- Always verify your answer by checking the relationship works in BOTH directions consistently
- If one operation does not work, immediately try squaring or cubing before moving on
- The relationship is always exact — no approximations in SSC CHSL
Key formulas
Difference pattern
B - A = D - C
When: When second number is always a fixed amount more than the first
Ratio pattern
B / A = D / C
When: When the second number is a fixed multiple of the first
Square pattern
B = A squared + k, same k for D = C squared + k
When: When numbers jump too large for simple multiplication
Cube pattern
B = A cubed or A cubed + k
When: When numbers are very large like 125, 216, 343
Product of digits
B = product of digits of A
When: When A is a 2-3 digit number and B seems unrelated at first glance
Worked examples
Example 1: 4 : 16 :: 7 : ? — Check: 4 squared = 16, so 7 squared = 49. Answer is 49.
Example 2: 3 : 28 :: 5 : ? — Check difference: 28 - 3 = 25, that is 5 squared. So 5 + 5 squared = 5 + 25 = 30. Answer is 30. Pattern is A + A squared.
Most Common Pattern Types in SSC CHSL
SSC CHSL recycles a small set of patterns year after year. Learning to recognize these on sight saves precious seconds. The moment you see the numbers, run through this mental checklist in order: simple difference, ratio, then squares, then cubes, then mixed.
- Type 1 — Square based: 5:25, 7:49, 11:121. Second number is square of first
- Type 2 — Square plus constant: 3:11 means 3 squared + 2 = 11. Find the constant
- Type 3 — Cube based: 4:64, 5:125. Second number is cube of first
- Type 4 — Difference of squares or cubes: 6:35 means 6 squared minus 1 = 35
- Type 5 — Sum of digits or product of digits: 23:6 means 2+3=5, wait that is 5 not 6, try 2x3=6. Yes product pattern
- Type 6 — Consecutive number operations: 5:30 means 5 x 6 = 30, product of consecutive numbers
Key formulas
Consecutive product
B = A x (A+1)
When: When second number is slightly more than A squared, check A x (A+1)
Sum of digits
B = sum of digits of A
When: When A is 2+ digit and B is small single digit
Worked examples
Example 3: 12 : 3 :: 24 : ? — Sum of digits: 1+2=3. So 2+4=6. Answer is 6.
Example 4: 5 : 30 :: 8 : ? — Pattern: 5 x 6 = 30, that is A x (A+1). So 8 x 9 = 72. Answer is 72.
Odd One Out variant of Number Analogy
SSC CHSL also asks you to find the pair that does NOT follow the same relationship as the others. Here you are given 4 pairs and must identify the odd pair. The method is the same — find the relationship in 3 pairs, the one that breaks the rule is your answer. Do not spend time trying to find a relationship in the odd one — confirm 3 pairs first.
- Check all 4 pairs for the same operation — square, cube, ratio etc.
- Three pairs will share one relationship, one pair will be the misfit
- If you are stuck, eliminate options — rule out pairs that clearly match first
- Common trick: one pair looks close but uses square instead of cube or vice versa
- Always double check your chosen odd pair — SSC examiners place the trap in obvious-looking options
Speed Strategy for Exam Hall
In SSC CHSL, Reasoning is timed tightly. Number Analogy should take you 20-40 seconds per question maximum. Use the DRSC mental checklist to avoid wasting time exploring wrong patterns.
- Step 1 — D: Check simple Difference (B minus A). Is it constant?
- Step 2 — R: Check Ratio (B divided by A). Is it a whole number?
- Step 3 — S: Try Squares. Is B equal to A squared or A squared plus/minus a small number?
- Step 4 — C: Try Cubes. Is B equal to A cubed?
- If all 4 fail, try digit sum or digit product — that is usually the last resort pattern in SSC CHSL
⚠ Common mistakes to avoid
- Stopping at the first pattern that partially fits — always verify the same pattern works perfectly before marking the answer
- Confusing square and cube patterns — 4:64 is cube (4 cubed = 64) but 4:16 is square (4 squared = 16). Do not mix them up under time pressure
- Ignoring the constant in patterns like A squared + k — many aspirants find the square but forget to add or subtract the constant in the second pair
- In Odd One Out questions, marking a pair as odd just because the numbers look big — always verify all 4 pairs mathematically
- Not checking digit sum vs digit product — 23:5 is digit sum (2+3=5) but 23:6 is digit product (2x3=6). One wrong assumption wastes the question
🧠 Memory aids
- Checklist mnemonic DRSC — Difference, Ratio, Square, Cube. Run this in order every single time. Think of it as Default Reasoning Saves Candidates.
- Squares to memorize up to 25: 1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,289,324,361,400,441,484,529,576,625. If a number in the pair matches one of these, square pattern is likely.
- Cubes to memorize up to 15: 1,8,27,64,125,216,343,512,729,1000. See a big jump in the pair? Think cubes first.
- Analogy trick — treat the first pair like a recipe. Identify exactly what was done to the first ingredient to get the second. Then cook the third ingredient the exact same way.
🎯 SSC CHSL exam tips
- SSC CHSL typically has 2-3 Number Analogy questions in the Reasoning section. They are usually Easy to Medium level — do not skip them hoping for easier ones later.
- Recent papers (2023-2024) show more square-plus-constant and consecutive-product patterns, moving away from pure ratio questions. Be ready for A squared + k type.
- Odd One Out number pair questions are increasingly common. Expect at least 1 such question. Practice identifying the misfit pair quickly.
- If a question takes more than 45 seconds, mark your best guess and move on. Do not let one Number Analogy block hurt your overall Reasoning score.
- Questions with 2-digit numbers almost always use digit sum or digit product patterns. This is a quick signal — if you see 2-digit numbers, try digit operations first instead of last.