A numeric code rule — Coding & Decoding Aptitude Question
A numeric code rule: If 5 = 30, 6 = 42 and 7 = 56, then 8 = ? Answer and worked solution on CodeKairo.
- Topic: Coding & Decoding
- Section: Logical Reasoning
- Difficulty: Medium
- Time target: 75 seconds
Question
If 5 = 30, 6 = 42 and 7 = 56, then 8 = ?
Options
- 64
- 68
- 72
- 80
Show the answer and the worked solution
Correct answer: C. 72
Worked solution
- The rule is n × (n + 1): 5 × 6 = 30, 6 × 7 = 42, 7 × 8 = 56.
- So 8 → 8 × 9 = 72.
Answer: 72.
The idea
Try n², n² ± n and n(n + 1) when a number maps to a larger one. Checking against all three examples confirms the rule.
Shortcut. The outputs rise by 12 and then 14, so the next rise is 16: 56 + 16 = 72, with no need to name the rule.
Common trap. "64" — seeing 8 and reaching for 8² by reflex; the examples fail that test at once, since 7 maps to 56, not 49.