Exponential and Logs:

1.) An earthquake off the coast to japan has a magnitude of 8.0 and it caused a tsunami. to the nearest tenth, determine the magnitude of an earthquake that is one half as intense as this earthquake. answer to nearest tenth.

2.) Imani invests $4942 in a retirement account with a fixed annual interest rate of 2% compounded 2 times per year. how long will it take for the account balance to reach $6931.54?

3.) A cup of coffee contains 160mg of caffeine. in a healthy adult, the mass, m grams, that remains after t hours is modelled by the function

m=160.(1/2)^0.2t

To the nearest half hour, how long will it take until only 20 mg of caffeine remains?