Two sets of numbers are given below. In each set of numbers, certain mathematical operation(s) on the first number result(s) in the second number. Similarly, certain mathematical operation(s) on the second number result(s) in the third number and so on. Which of the given options follows the same set of operations as in the given sets? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.) 18 – 36 – 72 – 107; 15 – 30 – 60– 95
- (a)30 – 60 – 90 – 115
- (b)25 – 50 – 100 – 125
- (c)22 – 44 – 88 – 123
- (d)11 – 22 – 66 – 101
Answer
Why
Correct — C. Rule: ×2, then ×2, then +35.
18 → 36 → 72 → 107: 18 × 2 = 36, 36 × 2 = 72, 72 + 35 = 107 ✓
15 → 30 → 60 → 95: 15 × 2 = 30, 30 × 2 = 60, 60 + 35 = 95 ✓
Now run option (c): 22 × 2 = 44, then 44 × 2 = 88, then 88 + 35 = 123.
All three operations land on the printed numbers, so 22 – 44 – 88 – 123 is the match → option (c).
Why the others are wrong
- (a)30 – 60 – 90 – 115 — The first step holds, 30 × 2 = 60, but the second adds 30 instead of doubling — doubling 60 gives 120, not the 90 printed.
- (b)25 – 50 – 100 – 125 — Both doublings work, 25 → 50 → 100, but the last step adds 25 instead of 35, and 100 + 35 is 135.
- (d)11 – 22 – 66 – 101 — 11 × 2 = 22 holds, then the row triples to 66 where the pattern doubles to 44. Its closing +35 is right, which is what makes it tempting.
Concept
These same-set-of-operations items give you two worked rows so you can separate a coincidence from a rule. Derive the rule from the first row, confirm it on the second, and only then touch the options.
Read each step as an operation, not as a difference. 18 → 36 is both ×2 and +18, but only ×2 also explains 36 → 72, and only an addition explains 72 → 107.
Once the chain is fixed as ×2, ×2, +35, every option is a three-line check. Run all three steps even after two of them fit, because option (b) fails only on the last one.
The stem's NOTE blocks digit work, so 107 may not be read as 1, 0 and 7. Every link has to be an operation on the whole number.
Key facts
- Both given sets run ×2, then ×2, then +35.
- In option (c) the chain is 22 × 2 = 44, 44 × 2 = 88, 88 + 35 = 123.
- The NOTE forbids splitting a number into its constituent digits.
Study next
Common traps
- Fixing the rule from the first two terms only, where ×2 and +18 both fit.
- Checking the two doublings and skipping the last step, which is where option (b) fails.
- Assuming the final step must also be multiplicative because the first two are.
Reasoning Q.3 of this shift prints the same whole-numbers NOTE, in slightly different words, and also asks you to test one arithmetic link against a whole row of numbers.
Related PYQs
No directly related past PYQ was found.