Explain simply why 60 is the correct answer to: It takes Matt 2 minutes per problem to do his math homework with a calculator and 5 minutes per problem without a calculator. If Matt's assignment has 20 problems, how much time will using a calculator save?. Explanation:
First find the time difference per problem: 5 minutes / problem - 2 minutes / problem = 3 minutes / problem. Then multiply that number by the number of problems to find the total time difference: 3 minutes / problem * 20 problems = 60 minutes.