8th Grade Functions: Battery Life
RULE
they planned to
Sam wants to take his tablet and phone on a car trip. An hour before they planne
leave, he realized that he forgot to charge the batteries last night. At that point
plugged in both devices so they can charge as long as possible before they left.
Sam knows that his tablet has 40% of its battery life left and that the battery charge
by an additional 12 percentage points every 15 minutes.
His phone is new, so Sam doesn't know how fast it is charging but he recorded the
battery charge for the first 30 minutes after he plugged it in. (see the table below)
Time charging (minutes)
10
20
30
Phone battery charge (%)
20
/
32
44
56
a. If Sam's family leaves as planned, what percent of the battery will be charged for
each of the two devices when they leave?!
b.
How much time would Sam need to charge the battery 100% on both devices?