In this number analogy question, select the related number from the given alternatives: 13 : 20 :: 17 : ?

Introduction / Context:
This number analogy question asks you to detect a simple arithmetic relationship that links 13 to 20 and then extend the same rule to 17. Identifying such patterns is an important part of quantitative aptitude because it trains you to see how numbers transform under basic operations.

Given Data / Assumptions:
- The first pair is 13 and 20.
- The second starting number is 17.
- The options are 25, 26, 27, and 28.
- We assume the rule involves standard operations such as multiplication and addition or subtraction and that it should be simple and consistent.

Concept / Approach:
A good strategy is to try a combination of multiplying by a small number and then adding or subtracting a constant. Notice that 13 * 2 equals 26, which is close to 20, and 13 * 2 - 6 equals 20 exactly. This suggests a formula of the form result = (number * 2) - 6. If this rule works for 17 as well and matches one of the answer choices, then it is the intended pattern.

Step-by-Step Solution:
Step 1: Multiply 13 by 2 to get 26.Step 2: Subtract 6 from 26, giving 20. So a possible rule is result = (number * 2) - 6.Step 3: Test whether any simpler rule like number + 7 works. 13 + 7 equals 20, but then 17 + 7 equals 24, which is not an option.Step 4: Now apply the rule result = (number * 2) - 6 to 17. First compute 17 * 2 = 34.Step 5: Subtract 6 from 34 to get 28.Step 6: Among the options, 28 is present as option D, so it is the correct answer.Step 7: The rule is consistent and simple, making it suitable for this analogy question.

Verification / Alternative check:
Confirm that the formula holds consistently. Using result = (number * 2) - 6, 13 gives 20 and 17 gives 28. If we tried a different pattern, such as result = (number * 2) - 8, then 13 would give 18, not 20. Similarly, a rule like number * 2 + any constant would not match both the given pair and one of the options. This confirms that (number * 2) - 6 is the most reasonable transformation.

Why Other Options Are Wrong:
- 25: This would come from 17 + 8, which is unrelated to the pattern used with 13.
- 26: This equals 17 + 9 or 17 * 2 - 8, which does not fit the transformation seen in the first pair.
- 27: There is no simple symmetric rule that maps 13 to 20 and 17 to 27 using the same operations.

Common Pitfalls:
Test takers sometimes rely on pure addition or subtraction without testing whether the same constant works for both numbers. Others may guess based on proximity to 34, the double of 17, instead of computing the exact rule. To avoid these issues, always derive a formula that exactly fits the given pair, then use it consistently on the second number and confirm that the result appears among the options.

Final Answer:
Using the pattern result = (number * 2) - 6, 13 maps to 20 and 17 maps to 28. Thus 28 is the correct answer.