there is 0.015 kilos in 15 grams. if each can weighs 0.015 and he gets paid 50p per KG. 0.015 X 66 will get you 1 kilogram! so you have 66 cans to get 1 kg worth of cans. so there is 15 dollars and each kg is worth 50p- so 66 cans is = 50p
and there is 2 KG per dollar so 15 X 2 is 30! and then 66 X 30 is 1980!
66 for each KG and 30 represents how many 50p's are needed for 1 dollar!
so that is 1980 cans to get 15 dollars!