Use a calculator to solve the problem. If k = 0.213, how long will it take a battery to reach a 50% charge? Assume that the battery was fully discharged when it began charging. Step 1 The length of time t required to charge a battery is given by t = - _ In 1 C , where k is a constant, C is the desired charge level desired charge level , and M is the theoretical maximum charge theoretical maximum charge Step 2 Substitute k = and C into the formula. M t = = Evaluate, rounding to the nearest tenth of a minute. min Thus, it will take approximately minutes for the battery to charge to 50% of capacity