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Number series (missing term): Differences follow triangular numbers. Given sequence: 5, 6, 9, 15, ?, 40 Hint: successive differences are 1, 3, 6, 10, 15, … Choose the correct missing number.

Q: Number series (missing term): Differences follow triangular numbers. Given sequence: 5, 6, 9, 15, ?, 40 Hint: successive differences are 1, 3, 6, 10, 15, … Choose the correct missing number.

Observation Differences: 6−5=1, 9−6=3, 15−9=6, ?−15=10, 40−?=15. These are triangular numbers (1, 3, 6, 10, 15 … with increments +2, +3, +4, +5). Compute Missing term = 15 + 10 = 25Check next: 40 − 25 = 15 (fits the pattern) Final Answer 25

Difficulty: Easy

Correct Answer: 25

Explanation:

Observation
Differences: 6−5=1, 9−6=3, 15−9=6, ?−15=10, 40−?=15. These are triangular numbers (1, 3, 6, 10, 15 … with increments +2, +3, +4, +5).

Compute
Missing term = 15 + 10 = 25Check next: 40 − 25 = 15 (fits the pattern)

Final Answer
25

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