Xiao Ming wants to choose one of the two kinds of lamps. One is a 10 watt energy-saving lamp, which costs 32 yuan; the other is a 40 watt incandescent lamp, which costs 2 yuan. The two kinds of lamps have the same lighting effect and the same service life. If the electricity charge is 0.5 yuan / kwh, which lamp do you choose to buy?

Xiao Ming wants to choose one of the two kinds of lamps. One is a 10 watt energy-saving lamp, which costs 32 yuan; the other is a 40 watt incandescent lamp, which costs 2 yuan. The two kinds of lamps have the same lighting effect and the same service life. If the electricity charge is 0.5 yuan / kwh, which lamp do you choose to buy?

When the lighting time is x hours, the cost is the same. From the question meaning: 32 + 0.5 × 0.01x = 2 + 0.5 × 0.04x, the solution is: x = 2000. Answer: when the lighting time is less than 2000 hours, choose incandescent lamp. When the lighting time is more than 2000 hours, choose energy-saving lamp

How to convert the brightness of incandescent lamp and energy-saving lamp? For example, how many watts of incandescent lamp is equivalent to the brightness of 15 watts of energy-saving lamp?

Multiply by 5 is to replace the brightness of the incandescent lamp, because the energy-saving lamp is 4 / 5 energy-saving than the incandescent lamp, that is to say, the wattage of an energy-saving lamp is equivalent to 1 / 5 of the incandescent lamp with the same brightness

The energy-saving effect of using energy-saving lamp is obvious. Generally, 15 Watt energy-saving lamp produces the same brightness as 60-80 watt ordinary incandescent lamp, but it can save electricity ()

This sentence is correct
Suppose that for every hour of electricity consumption:
The power consumption of 15W energy saving lamp is 15W × 1H = 0.015kwh
The power consumption of 60W incandescent lamp is 60W × 1H = 0.06kwh
In this way, one hour can save electricity
0.06kwh-0.015kwh=0.045kwh,
If you turn on the light for 10 hours every day, you can save a lot of electricity in a year

What is one degree centigrade equal to

The "unit length" of centigrade and Kelvin is the same, so in the conversion of temperature difference, one centigrade = 1 kelvin, centigrade and Kelvin form a linear function, t = t + 273.15