To find the efficiency of the radio, you divide the energy output (94.5 J) by the energy input (270 J), which gives you an efficiency of 0.35 as a decimal.
The efficiency of the radio can be calculated by taking the energy output in the desired form and dividing it by the total energy input, then multiplying by 100 to get a percentage, or leaving it as is for a decimal. In this case, we have an electrical energy input of 270 J and a sound energy output of 94.5 J.
The efficiency of a device is defined as the ratio of useful output energy to the total input energy. In this case, the useful output energy is the energy transferred electrically, which is 270 J, and the total input energy is the sum of the electrical energy and the energy transferred by sound, which is 94.5 J.
Efficiency = (Energy Output / Energy Input) = (94.5 J / 270 J)
Now, let's calculate the efficiency:
Efficiency = (94.5 / 270) = 0.35 (as a decimal)