Solved IB ACIO Question
A solved IB ACIO PYQ — decoded step-by-step.
Solve it the standard way once — then learn the shortcut.
Q · Missing Numbermedium · 45s
What number replaces the question mark?21, 18, 15, 12, ?
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.
Decreases by 3 each time; next is 9.
Final Answer: Option C — 9