Lesson 18: Using Functions to Model Battery Power 18.1: Devices
Think about an electronic device with a battery that you have to charge on a regular basis.
1. What device is it?
2.
When you are using the device, about how long does it take the battery to go from
100% charged until the time you plug it in again to recharge?
3.
About how long does it take to charge to 100% starting from 0% or nearly 0%?
4.
Suppose you plugged in your device when the battery was 50% charged.
How long do you think it would take to recharge the device to 100% compared to the
time it would take if the device was at 0%? Would it be exactly half the time, more than
half the time, or less than half the time it would take if starting from 0%?

Runners run around the school's football field. the cross country coach determines that the width of the field is seventy yards shorter than the length. part a write an expression that represents the perimeter of the football field. let x represent the length of the football field. include parentheses in your expression. next, write an equivalent expression that does not include parentheses. what property or properties did you use to simplify? explain. part b the cross country coach later determines that the length of the football field is 120 yards. all students must run five laps. using your answer from part a, determine the actual number of yards that each athlete must run in the tryouts. in order to make the team, students must complete the laps in 6 minutes. how quickly must they run each lap?