Simple Subtraction

This'll have to be my last post today lest I pass the 500 blogs a week limit. (I bet you didn't even know they had that limit.)

Anyways, I've found a use for subtraction: Calculating what time you ought to start your movies in order to end at a reasonable hour. For example: If you need to be done by 10:00 and your movie is 2 hours long, you should start no later than 8:00. I mention this because I have recently discovered that none of my siblings can do this.

Example 1: Heather recently tried to organize a watching of "Ever After" with the kids down to Grace (Bedtime=8:00). "Ever After" is 1 hr, 40 mins. What time should we start by?
Heather's Answer: 7:00.

Example 2: Alexie, Duncan, Andrew, David (Earliest bedtime: 9:00) all intended to watch a movie rental that needed to be returned as soon as possible. It was 100 mins (1 hr, 40 mins.) What time do we start by.
Alexie's and Andrew's Answer: Ignore Duncan and David trying to get it started at 7:00 so that David will be able to watch the whole thing. Send e-mails for thirty extra minutes, start at 7:30.

The reason I brought this up was because last night David helped with the Walk for Life. (fighting abortion.) David and Andrew had an one-hour movie for that night so I made sure to get David back before 8:00 so he could watch it. When we got back, we were immediately greeted by Andrew who said to David (exact quote): "David, because you went walking for life we can not watch our movie tonight." David was very upset. Now this strikes me as odd because Andrew: a) doesn't care whether anyone gets to bed on time. b) Always starts his movies way too late. c) Was wrong because they did manage to watch it all and end before 9:00.

The only thing that Andrew did by saying that was to make David feel bad for doing the Walk for Life, something which is one hundred times more important than watching a movie or doing computer projects.