A renewable energy facility stores electricity in three separate battery modules: Module , Module , and Module . The ratio of the initial energy stored in Module to Module is , and the ratio of the initial energy stored in Module to Module is . Each module discharges its stored energy at a constant individual rate. Operating alone, Module can completely discharge its initial stored energy in hours. Module discharges energy at a rate greater than Module , and Module discharges energy at a rate less than the combined discharge rate of Modules and . If all three modules begin discharging simultaneously, how many hours will it take to completely discharge the total initial energy stored across all three modules?
- A3.5 hours
- 4 hoursAnswer
- C5.25 hours
- D6 hours
- E7.5 hours
Answer
4 hours
To find the total time required, first unify the two given ratios. Since and , express both ratios with a common value for (). This yields , so total energy is . Next, determine rates in terms of : Module discharges in hours, so its rate is units/hr. Module discharges at a rate greater than Module , giving units/hr. The combined rate of and is units/hr. Module discharges at less than this combined rate, giving units/hr. The simultaneous discharge rate of all three modules is units/hr. Dividing total energy by gives exactly 4 hours.
Step-by-Step Solution
Key Concept
Combining multi-part ratios into a unified scale and calculating combined work rates with percentage adjustments