A homeowner empties her hot water heater every 36 days and changes the filter in the heat pump every 48 days. She did both on Friday September 17, 2012. When again will she do both on the same day? (give the day of the week, the date, month, and year)

Answer 1

This is like finding the LCM of 36 and 48

36 = 2x2x3x3
48 = 2x2x2x2x3

LCM = 2x2x2x2x3x3 = 144

So it will happen 144 from Sept 17, 2012

BTW, Sept 17, 2012 was a Monday , not a Friday , so I will let you sort out the rest.

http://www.searchforancestors.com/utility/dayofweek.html