IKMC 2027 - Grades 3-4 - Self-study SET 17 - Thematic Batch 3 Question 3

Four numbered gears are arranged as shown. Gear 1 has 40 teeth, gear 2 has 20, gear 3 has 80 and gear 4 has 10. When gear 1 makes one complete turn, how many turns does gear 4 make?