What were most of the elements discovered when mendeleev developed his original periodic table?
a. gases
b. radioactive
c. liquids
d. solids

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?

The number of passengers who arrive at the platform of a subway station for the 10 am train is a random variable with a mean of 120 and a variance of 16. find the lower bound of the probability that there will be between 100 and 140 passengers (round off to second decimal place).