Lisa is standing on a dock beside a lake. She drops a rock from her hand into the lake. After the rock hits
the surface of the lake, the rock's distance from the lake's surface changes at a rate of -6 inches per
second. If Lisa holds her hand 5 feet above the lake's surface, how far from Lisa's hand is the rock 6
seconds after it hits the surface?
The rock is
inches away from Lisa's hand.

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.