<prompt> Human: I live with my boyfriend and room mate so we have been splitting rent and utilities 3 ways. She said she would move out by the end of today so the 18th and she would still pay me for her part of the rent and stuff. I want to ration it out as evenly as i can for the 18 days she spent here, can anyone provide me a formula to use when calculating her share of the bills please? For example Im pretty sure this months rent will come out to 1008 and SRPelectricity could possibly be 190.Our lease is up the end of November so I told her I would be giving our 30-day notice on October 1st and to make sure she left her keys, am I missing anything? Thanks!  <response>: Divide total by 30 days in September to determine costday and then divide by three to determine her cost per day three of you each, equally, then multiply the number you get as a perday amount by the days she stays. 