1. COURSE 2 LESSON 4-7 4-7 Kayla is bringing brownies to the sports banquet. She needs to be there by 7:15 P.M. It will take Kayla’s family h to walk from their apartment to school. The brownies take hour to make, hour to bake, and 1 hours to cool. What is the latest time Kayla can start making the brownies so they will be cool before she leaves for the banquet? 1414 1414 1212 1212 Your goal is to find out the latest time Kayla can start making brownies and then arrive at the banquet at 7:15. It takes h to walk to the banquet, h to make the brownies, h to bake them, and 1 h for them to cool. 1414 1414 1212 1212 Try, Check, and Revise and Work Backward

2. COURSE 2 LESSON 4-7 4-7 (continued) Method 1 Try, Check, and Revise Choose a value that makes sense and then check it. If your first check is not a solution, use the result to revise your estimate. Make Brownies Bake Brownies Cool Brownies Leave Home Arrive at Banquet Result 5:30 P.M. 5:45 P.M. 6:15 P.M. 7:45 P.M. 8:00 P.M. 45 min late Starting the brownies at 5:30 P.M. causes Kayla to arrive 45 min later than intended. Therefore, by starting the brownies 45 min earlier, at 4:45 P.M., Kayla will arrive at 7:15 P.M. Try, Check, and Revise and Work Backward

3. COURSE 2 LESSON 4-7 4-7 (continued) Method 2 Work Backward You know that the series of events must end at 7:15 P.M. It makes sense to work backward to find when Kayla must start making the brownies. Working backward shows that by starting the brownies at 4:45 P.M. Kayla will get to the banquet at 7:15 P.M. Try, Check, and Revise and Work Backward

4. COURSE 2 LESSON 4-7 4-7 (continued) Subtract 2 h from 7:15 P.M. and you find that Kayla must start making the brownies at 4:45 P.M. The answer checks. It takes h to make the brownies, h to bake, and 1 h to cool. It takes h to walk to the banquet. Add these times to find the total time from when Kayla starts the brownies to when she arrives at the banquet. 1414 1212 1212 1414 1414 + + 1 + = 2 h 1212 1212 1414 1212 1212 Try, Check, and Revise and Work Backward

5. You need to be in school at 7:45 A.M. It takes you h to shower and brush your teeth, 10 min to get dressed, and 20 min to eat breakfast. The bus, which picks you up outside your house, takes h to get to school. What is the latest time you should get up in the morning? COURSE 2 LESSON 4-7 4-7 3434 6:00 A.M. 1212 Try, Check, and Revise and Work Backward