Question

A battery was charged. When the charging began, it was 23 percent full. After 30 minutes of charging, the battery was 89 percent full. how fast did the battery charge and how long did it take?

Answer 1

QUESTION:

A battery was charged. When the charging began, it was 23 percent full. After 30 minutes of charging, the battery was 89 percent full. how fast did the battery charge and how long did it take?

Solution :

Given

• Initial amount of charge = 23%
• Amount after charge = 89%

procedure

Let the rate of charging be r .

r = (change in charge level) / (time interval) = (89% - 23%) / (30 min) = 2.2 % per minute

charge = (rate of charging)(time) + (initial charge)

100% = r*t + 23%

100% = (2.2 %/min)t + 23%

Solve for t and get

t = [(100 - 23) / 2.2]

Answer = 35 min