Rohan can drive to his uncle's place in 6 hours at an average speed of 55 miles per hour. In how many hours sooner does he reach his uncle's place if he drives at an average speed of 65 miles per hour?

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g