Express efficiency as a decimal.

Efficiency is a measure of how effectively energy is converted from one form to another, expressed as a decimal. It is calculated by dividing the useful energy output by the total energy input. For example, if a device uses 100 J of energy and produces 80 J of useful work, its efficiency would be 0.8 (or 80% when expressed as a percentage). Understanding efficiency as a decimal helps in comparing the performance of different devices and processes, highlighting the importance of minimizing wasted energy to improve overall effectiveness.