How to use: Find Greatest Common Divisor (GCD) or Least Common Multiple (LCM) of two numbers. Select Type: GCD (largest number dividing both) or LCM (smallest number divisible by both). Enter First Number and Second Number. Examples: GCD(12, 18) = 6 (largest divisor of both). LCM(12, 18) = 36 (smallest multiple of both). GCD(8, 12) = 4. LCM(4, 6) = 12. Applications: GCD for simplifying fractions (reduce 12/18 to 2/3 using GCD=6), finding common measurements. LCM for scheduling (events repeat every X and Y days, when do they align?), adding fractions (find common denominator). Essential for elementary math, number theory, and practical scheduling problems.