The starting amount of radioactive iodine-131 was 250 g. the half-life is 8 days. when leslie measured the amount, she measured 15.625 g of radioactive iodine. how many days have elapsed between measurements?

a. 16

b. 24

c. 32

d. 64

The famous scientist galileo galilei did several experiments with sloping planes, which he rolled metal balls down so that he could study motion. by changing the slope, he could study how the speed at which the ball rolled was affected. what was the independent variable in galileo's experiment? a. the speed of the ball b. the slope of the plane c. whether the ball moved d. what the ball was made of