Measuring Elapsed Time Unit of Study 9 : Measuring Time Global Concept Guide: 3 of 3

Content Development  Approximately 4 days should be spent on calculating elapsed time using different strategies.  Students need to understand how many minutes are in an hour and how many minutes until the next hour.  Avoid having students use the traditional addition and subtraction algorithms to calculate elapsed time. They will not work in all cases.  As a general model for elapsed time problems, suggest students use an open number line. Its not important to be overly prescriptive in telling students how to use the number line since there are various alternatives (Dixon, 2008).  Continue to require students to specify times using A.M. and P.M.

Content Development  Provide students with elapsed time using various formats:  Start unknown: Zach and his family are going to Miami Beach. Their airplane leaves at 9:15 A.M. They need to arrive at the airport one hour before their flight. It take 25 minutes to get to the airport. The family needs 45 minutes to get ready to leave. At what time should Zach’s family get up? (p. 527 ULP)  End Unknown: Tom and his family arrived at the Kennedy Space Center at 10:30 am. They left 6 hrs. 30 mins. later. At what time did they leave the space center? (p. 526 #8)  Elapsed Time unknown: A movie at the Space Center began at 1:15 P.M. and ended at 1:55 P.M. How long did the movie last? (p. 524 Find Elapsed Time in Minutes)

Day 1  The focus of Day 1 is to determine what elapsed time means.  The students should be using open number lines and analog clocks to calculate elapsed time.  Students should first learn how to count elapsed time in hours and then in minutes. Eventually, they should combine the two skills to calculate elapsed time in both hours and minutes.  Sample Task: P. 523 Unlock the problem. Connect using an analog clock to solve this problem to jumps on the number line.

Day 2  The focus of Day 2 is how a number line can help you solve elapsed time problems.  Sample Task: p. 526 # 9  John started reading his book about outer space at 6:30 pm. He read for 1 hour and 25 minutes. At what time did John stop reading his book?  Students should be allowed to utilize the number line in any way that makes sense to them when solving elapsed time problems.

Day 3  The focus of Day 3 is connecting a number line with a clock face when solving elapsed time problems.  Students should notice that a number line and a clock face both are versions of the linear model.  Sample Task: p. 526 Write Math  Tom’s family toured the astronaut hall of fame from 2:15 P.M. until 3:20 P.M. Explain how you know that the tour was less than 2 hours using a clock face or a number line. (Text in red shows modifications to Go Math! Problem.)  Facilitate a discussion connecting the multiple strategies that could be used to solve this problem.

Day 4  The focus of Day 4 is using calendars and timelines to answer elapsed time problems.  Sample Tasks:  Calendar: The first day of summer is the longest day of the year. In 2010 it was on June 21 st. 8 weeks and 4 days earlier was Earth Day. Oh what day was earth day? (P. 533 #7)  Timeline: Julia turned 8 years old 2 months before she started 3 rd grade in In what year was Julia born? (P.533 ULP)

Enrich/Reteach/Intervention  Reteach:  TE p. 523B Reteach Activity provides students with pre-labeled number lines and deals with time to the hour.  R107 Students are given a start and end time as well as a blank number line and asked to calculate the elapsed time.  Enrich:  TE p. 523B Students input missing information in a Flight schedule based on departing times, travel times, and arrival times.  TE p. 527B Students plan a party (including activities and start, elapsed, and end times) and write word problems that can be solved using their schedule.