Alaptop can convert 400j of electrical energy into a 240j of light and sound. what is the efficiency? where does the rest of the energy go?

Efficiency = (Wanted) energy out ÷ energy in × 100

Energy in = 400J
Wanted Energy out = 240J

Energy cannot be used up, only transferred, so the remaining energy is most likely to be transferred into unwanted energy (loss of energy) such as heat energy.

Efficiency = 240 ÷ 400 × 100
Efficiency = 0.6 × 100
Efficiency = 60%

Ihope you get it right bro