If 5 = 15, 6 = 24 then 7 = _____?

The correct answer is 35. This question follows a simple numerical pattern in which each number is multiplied by one less than itself. For example, 5 = 5 × (5 − 2) = 5 × 3 = 15 and 6 = 6 × (6 − 2) = 6 × 4 = 24. Applying the same rule to 7 gives 7 × (7 − 2) = 7 × 5 = 35. Therefore, the missing value is 35. Such pattern-recognition questions are commonly asked in intelligence and aptitude tests to assess logical reasoning rather than mathematical formulas.

When solving number series or analogy questions, it is important to identify the relationship between the given numbers before attempting the next value. In this case, the multiplier increases by one as the original number increases: 5 × 3 = 15, 6 × 4 = 24, and 7 × 5 = 35. Recognizing this consistent rule leads directly to the correct answer without requiring complex calculations. Pattern-based reasoning is widely tested in competitive examinations because it measures analytical thinking and problem-solving ability.

Why the other options are incorrect:

• 30 is incorrect because it does not follow the multiplication pattern established by the previous values.
• 40 is incorrect because no valid mathematical relationship from the given examples produces this result.
• 45 is incorrect because it does not satisfy the consistent rule of multiplying the number by (number − 2).