The diameter of a small gear is 16 cm. This is 2.5 cm more than 1/4 of the diameter of a larger gear. What is the diameterof the larger gear?
16 cm - 2.5 cm = 13.5 cm, which is 1/4 of the diameter of the large gear. Take 13.5 cm * 4, and you have the diameter of the large gear, which is 54 cm.