Abattery was charged. when the changing began, it was 23 percent full. after 30 minutes of charging, the battery was 89 percent full. how fast was the battery charged?

Before it charged, the battery was at 23%. In half and hour, it went to 89%. So, it rose 89-23, or 66% in half an hour. Now that we know how much it rose and that there are 30 mins in half an hour, we have to divide 66% by 30 to figure out the answer.

66/30 is 2.2. 

So, the battery rose at 2.2% per minute. 

Hope this helps!

The answer is part a: use