Below are given two sets of numbers. In each set of numbers, a certain…
2026
Below are given two sets of numbers. In each set of numbers, a certain mathematical operation on the first number results in the second number. Similarly, certain mathematical operation on the second number results in the third number and so on. Which of the given options follows the same set of operations as in the question?
(NOTE – A two/three-digit number cannot be broken into individual digits for operations e.g. if 37 is followed by 10, the operation cannot be 3+7 as a two-digit number cannot be broken into individual digits)
31 - 217 - 434 - 436
11 - 77 - 154 - 156
Answer: C. 20 - 140 - 280 - 282 — Concept: In a number-analogy chain a fixed sequence of arithmetic operations is applied to each term to produce the next term. The task is to discover that…
- A.
22 - 154 - 770 - 772
- B.
20 - 125 - 375 - 378
- C.
20 - 140 - 280 - 282
- D.
25 - 200 - 600 - 602
Attempted by 32 students.
Show answer & explanation
Correct answer: C
Concept: In a number-analogy chain a fixed sequence of arithmetic operations is applied to each term to produce the next term. The task is to discover that sequence from the chains given in the question and then find the option chain that reproduces the identical sequence, operation by operation, in the same order. Because a multi-digit number may not be split into its digits, every operation must act on the whole number.
Application: Read the first given chain one step at a time.
31 × 7 = 217
217 × 2 = 434
434 + 2 = 436
The second given chain confirms the very same three steps.
11 × 7 = 77
77 × 2 = 154
154 + 2 = 156
So the rule for the chain is: multiply by 7, then multiply by 2, then add 2.
Cross-check: work out the step-to-step operations inside each option chain and compare them with this rule.
Chain | Step 1 | Step 2 | Step 3 |
|---|---|---|---|
22 - 154 - 770 - 772 | × 7 | × 5 | + 2 |
20 - 125 - 375 - 378 | × 6.25 | × 3 | + 3 |
20 - 140 - 280 - 282 | × 7 | × 2 | + 2 |
25 - 200 - 600 - 602 | × 8 | × 3 | + 2 |
Only the chain 20 - 140 - 280 - 282 matches the rule at every step: 20 × 7 = 140, 140 × 2 = 280 and 280 + 2 = 282.
Method tip: always test the operations in the fixed order set by the question chain; a chain that matches the first step but departs at a later step does not follow the same set of operations.