Solved IB ACIO Question
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Q · Missing Numbermedium · 45s
Identify the missing number:1, 3, 6, 10, 15, ?
TopicMissing Number
Question Typemultiple choice
Difficultymedium
Marking+1 / −0.25
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained - no skipped algebra.
These are triangular numbers (n(n+1)/2) or differences are consecutive integers:3−1 = 2, 6−3 = 3, 10−6 = 4, 15−10 = 5 → next difference = 6
So, 15 + 6 = 21
Final Answer: Option B - 21