A 20-gallon bathtub is to be filled with water that is exactly 100°F. The hot water supply is 175°F and the cold water supply is 20°F. When mixed, the temperature will be a weighted average based on the amount of each water source in the mix. How much of each should be used to fill the tub as specified?

Sawsan recorded the favorite sport of students at her school. she surveyed 200 students. how many students chose tennis?

There are 8 movies that you would like to see currently showing in theatres. in how many different ways can you choose a movie to see this saturday and one to see this sunday?

The biologist has a second culture to examine. she knows that the population of the culture doubles every 15 minutes. after 1 hour and 15 minutes, her assistant found that 80,000 bacteria were present. a) what was the size of the initial population? b) predict the size of the culture at t=3 hours. what was the size of the population at 40 minutes? explain and justify your answers. c) create a graph of the population as a function of time. find an equation that can be used to predict the size of the population at any time t. d) examine the rate at which the bacteria culture is growing. how fast is the culture growing after 1 hour? after 1.5 hours? after 2 hours? use a time interval of h = 0.01 hours to estimate these rates. interpret these rates in terms of the context of the problem situation. how do these three rates compare?