math
posted by nick .
If every 6th customer gets a coupon for free fruit snacks and every 9th customer gets a coupon for free fruit juice which customer will be the first to get both free fruit and free juice?

what is the lowest common multiple of 6 and 9 ?

My son has this question tonight for homework. I think the answer is the 18th person would get both coupons. I made a diagram. 5xs then a F for the free fruit coupon, i went up to 4 groups then a F. then i went back and counted to the ninth person and put a j for juice above it. The 18th person had both a j and a f.
xxxxxFxxxxxFxxxxxxFxxxxxF, then count 9, and put a j for juice above it. The 18th person has both coupons.