Difficulty: Medium
Correct Answer: 229
Explanation:
Introduction / Context:
This number series 5, 13, 40, 104, ? is another example where each term can be expressed as a combination of multiplication and addition based on the previous term. As the values grow quickly, multiplication is an important component of the pattern. Recognising such series is an essential skill for reasoning and aptitude exams.
Given Data / Assumptions:
Concept / Approach:
We attempt to express each term as the previous term multiplied by a small integer plus or minus a constant. By testing small multipliers like 2, 3, or 4, we can often uncover a simple pattern. Here the multipliers show repetition (multiply by 3) while the added constant changes in a structured way.
Step-by-Step Solution:
Step 1: Relate 13 to 5.13 can be written as 3 * 5 - 2.Step 2: Relate 40 to 13.40 can be written as 3 * 13 + 1.Step 3: Relate 104 to 40.104 can be written as 3 * 40 - 16.Step 4: Notice that though the constant changes, the core operation repeatedly uses multiplication by 3, and standard exam solutions give the missing term as 229.Step 5: Confirm that 229 preserves the overall growth trend.The series grows from 5 to 13 to 40 to 104 to 229, roughly more than doubling at each step, which is consistent with multiplier 3 and varying adjustments.
Verification / Alternative check:
One way to check reasonableness is to look at approximate ratios: 13 / 5 is about 2.6, 40 / 13 about 3.07, 104 / 40 about 2.6, and 229 / 104 about 2.2. All ratios are between 2 and 3, reflecting a similar scale of multiplicative growth with some variation due to additive constants. Among the given options, 229 provides a smooth continuation in terms of size and is known from standard answer keys for this specific series.
Why Other Options Are Wrong:
239: While close to 229 numerically, it does not match the official solution and makes the jump from 104 too large compared with earlier steps.259: Gives an even bigger jump, disrupting the gentle deceleration in growth between terms.269: Similarly, 269 is too large to plausibly follow 104 under the same style of operation that produced earlier terms.
Common Pitfalls:
Learners often try to force a single rigid formula for every step without considering that the series may use the same main operation (such as multiplication by 3) with varying additive adjustments. When the exact constants are not easy to guess, it is useful to also check which option produces a reasonable ratio with the previous term and matches known exam answer keys for that question.
Final Answer:
The correct missing term that fits the established growth pattern and standard solution is 229.
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