You play your Xbox 360 every day for a month. Each week you realize that every time you play, your battery lift goes down by 5% each week. Say you don’t play for two weeks, how much %___ are you saving a week by not playing.

If you save 5% the first week you are down to 95%

If you then save 5% of that the second week you are down to 95% of 95% = .9025 or at 90.25% of full charge which means you saved (1/2)(1-.9025)(100) = 4.875% per week on the average. That is hardly fourth grade. It is more in the compound interest regime of math.

To calculate the percentage you are saving per week by not playing, we need to determine the battery loss per week while you are playing, and subtract it from the total battery loss per week.

Given that your battery life goes down by 5% each week you play, the battery loss per week can be calculated as 5% of the total battery life.

So, let's assume the total battery life at the beginning of the month is 100%.

Week 1: Battery loss = 5% of 100% = 5%
Week 2: Battery loss = 5% of 95% (remaining battery life from week 1) = 4.75%
Week 3: Battery loss = 5% of 90.25% (remaining battery life from week 2) = 4.5125%
Week 4: Battery loss = 5% of 85.7375% (remaining battery life from week 3) = 4.286875%

To find out the percentage you are saving per week by not playing for two weeks, we need to subtract the battery loss per week when you were playing from the battery loss per week calculated above.

Total battery loss per week = Battery loss in Week 4 = 4.286875%

Percentage saved per week by not playing = Battery loss per week when playing - Total battery loss per week
= 5% - 4.286875%
= 0.713125%

Therefore, by not playing for two weeks, you would be saving approximately 0.713125% of your battery each week by not playing.