A chemist has 10% and 40% solutions of acid available. How many liters of each solution should be mixed to obtain 120 liters of 15% acid solution?

Jeffery conducted a survey in his school and found that 30 of the 50 eighth grade students' favorite subject is mathematics. based on the results, jeffery concluded that out of the 200 students in his school, 120 students' favorite subject is mathematics. select the statement that is true about jeffery's conclusion. a. jeffery's conclusion is not valid because the sample was biased since only 200 students were surveyed. b. jeffery's conclusion is valid because the sample was random since all of the students were eighth grade students. c. jeffery's conclusion is valid because the sample was random. d. jeffery's conclusion is not valid because the sample was biased since all of the students were eighth grade students.

Which of the following three dimensional figures has a circle as it’s base

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?