An energy-saver light-bulb of 11w gives the same illumination as a conventional 60w light-bulb. a typical light-bulb is used on average for five hours a day, how much energy is saved per year by one light-bulb? 2. if each household used eight such light-bulbs, and there are 20 mi- lion households in a country, how much energy would that country save annually?

882000 J

51508800000 Joules

Explanation:

First  we need to convert the units

11 W = 11 J/s

60 W = 60 J/s

5 hours = 5×60×60 = 18000 seconds

The amount of power saved

60-11 = 49 W = 49 J/s

The amount of energy saved in 5 hours in a day

49 J/s × 18000 s = 882000 J

Energy saved in one day is 882000 J

There are 20 million households with each of them having 8 light bulbs in the country

So, energy saved in one year would be

882000×8×20×10⁶×365 = 51508800000 Joules

Energy saved in one year is 51508800000 Joules

a.

explanation:

see earlier answer