7. The equation for radioactive decay is P = (0.5)/H, where P is the fraction of a substance with half-life H remainin radioactive after a period of time, t. A given substance has a half-life of 3000 years. After t years, one sixth of th
original sample remains radioactive. Find t, to the nearest thousand years.

There are two major tests of readiness for college: the act and the sat. act scores are reported on a scale from 1 to 36. the distribution of act scores in recent years has been roughly normal with mean µ = 20.9 and standard deviation s = 4.8. sat scores are reported on a scale from 400 to 1600. sat scores have been roughly normal with mean µ = 1026 and standard deviation s = 209. reports on a student's act or sat usually give the percentile as well as the actual score. the percentile is just the cumulative proportion stated as a percent: the percent of all scores that were lower than this one. tanya scores 1260 on the sat. what is her percentile (± 1)?