Question

Charles has been assigned several chores around the house he washed the supper dishes every fifth day, he takes out the trash every other day, and he vacuumes the house every seven days. How often does he have to do all three things on the same day?

Answer 1

This question is about the GREATEST COMMON FACTOR. 

Supper Dishes: 5      10         15         20       25           30          35 

Trash: 1        3           5          7             9          11      13            15         17         19      21       23       25          27           29           31        33         35

Vacuums the House: 7         14          21         28         35            42

He will have to do all three chores on the same day every 35 day.