Chi needs some school supplies for 3 classes. he has tokens to use in the machine at school. he bought notebook paper for 60 tokens, a pen for 15 tokens, and 2 pencils. if the pen is 3 times the price of 1 pencil, how many tokens do 2 pencils costs?

Among the most famous of all meteor showers are the perseids, which occur each year in early august. in some areas the frequency of visible perseids can be as high as 40 per hour. given that such sightings are poisson events, calculate the probability that an observer who has just seen a meteor will have to wait at least five minutes before seeing another.