The Richter scale is used for measuring the magnitude of an earthquake.
The Richter magnitude is given R = 0.67log(0.37E) + 1.46 where E is the
energy (in kilowatt hours) released by the earthquake. If an earthquake
release 15,500,000,000 kilowatt hours of energy, what is the earthquake's
magnitude?

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.