math
posted by ryan on .
Anita does laundry every other day. Every five days she changes sheets. Every 15 days she dusts. If she does all three chores today, how many days will it be before she does them all on the same day again?

30 days later. this is like least common multiples... 2, 5, 15. the least common multiple is 30.

Today is Day 1.
She does laundry on days 1, 3, 5, 7, 9, etc.
She changes sheets on days 1, 6, 11, 17, 21, 16, 31, etc.
She dusts on days 1, 16, 31, etc. 
She changes sheets on days 1, 6, 11, 16, 21, 26, 31, etc