Missing Number
🔒 Log in to trackmedium importance~1-2 Q in Tier 12 formulas⚡ 5 shortcuts3 subtopics
Every formula in this topic, grouped by subtopic. Print it and pin it above your desk.
How missing-number puzzles work
Rule confirmation
f(a_1,b_1)=c_1 \ \text{and} \ f(a_2,b_2)=c_2 \Rightarrow \text{rule } f
Two agreeing instances pin the rule; one instance pins nothing.
Common families
a+b,\ a-b,\ a \times b,\ ab \pm k,\ (a \pm b)k,\ a^2 \pm b,\ \text{digitsum}
Test sums/products first — they cover ~80% of CGL puzzles.