Question

An energy efficient light bulb uses 15 W of power for an equivalent light output of a 60 W incandescent light bulb. How much energy is saved each month by using the energy efficient light bulb instead of the incandescent light bulb for 4 hours a day? Assume that there are 30 days in one month

A. 7.2 kW⋅hr
B. 21.6 kW⋅hr
C. 1.8 kW⋅hr
D. 5.4 kW⋅hr
E. 1.35 kW⋅hr

Answer 1

Answer: (d)

Step-by-step explanation:

Given

15 W is equivalent to 60 W light that is, it save 45 W

So, for 4 hours it is,
`4* 45=180\ W.hr`

For 30 days, it becomes

`\Rightarrow 180* 30=5400\ W.hr\\\Rightarrow 5.4\ kWh`

Thus,
`5.4\ kWh` is saved in 30 days

option (d) is correct.