For similar light intensity, compact fluorescent bulbs use about 25% of the energy of incandescent bulbs. let's say you replaced a bulb of 40 w with a fluorescent bulb and that your utility charges $0.15/kw-hour. how many dollars would you save in electricity in the 10,000−hour lifetime of the bulb?

Hope the image of the frequency formula

Radon-222 or rn-222 has a half-life of 3.82 days. to determine the fraction of an original sample of rn-222 that remains unchanged after 7.646 days, we calculate the amount of rn-222 remaining after 7.646 days and divide it with the original amount. using 1 gram as a basis and using half-life calculation methods, we can determine that  0.249 or 0.25  grams of rn-222 will remain, and thus the fraction remaining is 0.25 or 1/4.