Classroom Library
Learn Least Common Multiple & Number Theory
Every guide below is written the way we explain these ideas at a whiteboard: concrete numbers first, plain-English steps second, and zero filler. Pick a topic below to get started.
How to Find the Least Common Multiple (All 4 Methods Compared)
Walk through listing multiples, prime factorization, the two-number GCF formula, and the cake division ladder—plus a decision chart for when to use each.
LCM vs. GCF: How to Tell Them Apart (With Side-by-Side Examples)
Why 'Least' makes a bigger number and 'Greatest' makes a smaller number, demonstrated on the exact same numbers (18 and 24).
10 Real-Life LCM Word Problems with Step-by-Step Solutions
Bus schedules, square floor tiles, meshing gear teeth, traffic lights, track laps, and lighthouse beacons—all solved step by step.
Using LCM to Add and Subtract Fractions with Unlike Denominators
How turning the LCM of two denominators into the Least Common Denominator keeps your fraction numerators small and manageable.
How to Find the LCM of Fractions (Formula & Proof)
Need the smallest number that two whole fractions divide into cleanly? Learn the formula LCM(a/b, c/d) = LCM(a, c) ÷ GCF(b, d).
7 Common Mistakes Students Make When Finding the LCM
From adding exponents instead of picking the highest power to misusing the 3-number GCF formula, here is how to catch errors before turning in a test.
Mental Math LCM Tricks & Shortcuts
Spot coprime numbers, consecutive integers, and direct multiples so you can find the LCM in your head in two seconds.