Derek must choose a four digit PIN number. Each digit can be chosen from 0-9. How many different pins can Derek choose?

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

You eat 8 strawberries and your friend eats 12 strawberries from a bowl. there are 20 strawberries left. which equation and solution give the original number of strawberries?

The two square pyramids are similar. find the total volume of both pyramids if the ratio of their surface areas is 9/16