An unknown radioactive element decays into non-radioactive substances. In 740 days the radioactivity of a sample decreases by 33 percent.

(a) What is the half-life of the element?

(b) How long will it take for a sample of 100 mg to decay to 59 mg?

Kevin has a spinner that has 10 equal sections and 2 sections of each color—red, blue, green, yellow, and purple. kevin spins the spinner 180 times. kevin determines about how many times the spinner will land on red or green, and his work is shown below. -kevin has the formula reversed; it should be the total number of sections over the number of red or green sections. -kevin should have used a 4 in the numerator because there are 2 red sections and 2 green sections. -kevin should multiply by the number of sections in the spinner rather than the total number of spins. -kevin calculated the prediction correctly and did not make any mistakes.