Number Series — Doubling Plus Increasing Addend Find the next number in the series: 6, 13, 28, 59, ?
-
A111
-
B113
-
C114
-
D122
Answer
Correct Answer: 122
Explanation
Introduction / Context:This series grows by approximately doubling and then adding a steadily increasing small number. Spotting the pattern in the additive term is the key.
Given Data / Assumptions:
- Terms: 6, 13, 28, 59, ?
- Look for a rule like next = 2 * current + k, with k increasing by 1 each step.
Concept / Approach:Verify whether each term equals twice the previous plus an increment that grows linearly by 1. This is a common construction in aptitude sequences.
Step-by-Step Solution:6 → 13: 6 * 2 + 1 = 1313 → 28: 13 * 2 + 2 = 2828 → 59: 28 * 2 + 3 = 59Therefore, next should be 59 * 2 + 4 = 118 + 4 = 122
Verification / Alternative check:The additive constants are 1, 2, 3, then 4, confirming a simple linear increase paired with doubling. Hence 122 fits exactly.
Why Other Options Are Wrong:
- 111, 113, 114: None match the precise rule of doubling and adding 4 to 59.
Common Pitfalls:Guessing based on rough doubling without checking the consistent incremental addend. Always compute term-by-term to confirm.
Final Answer:122