Euclid and the shrinking problem In the Elements, written in Antiquity, Euclid presented a procedure for finding the greatest common divisor. Instead of listing all the divisors, we can work with smaller and smaller divisions and remainders. Your turn to investigate: Investigate 24 and 18: 24 = 1 × 18 + 6; then 18 = 3 × 6 + 0. What was the last nonzero remainder? Compare with the square explorer in class. Discover the historical source on MacTutor, from the University of St Andrews.