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AKS: 4MA.D.6 measure time and objects that exist in the world to solve real-life, mathematical problems and analyze graphical displays of data to answer relevant questions (4.MDR.6).
Learning Target: I can solve problems involving elapsed time to the nearest minute.
Activating Strategy
Activating Strategy
Bertram went swimming for 53 minutes.
Choose two clocks. One clock will represent the time Bertram began swimming. The second clock will represent the time Bertram finished swimming. The elapsed time from beginning to ending time is 53 minutes.
Observe the clocks - Determine two clocks showing the beginning and ending times for the elapsed time of 53 minutes.
Be ready to turn and talk about your mathematical thinking.
Make a 4-square page in our math journals to answer Warm-Up questions using SLIDE 102.
Mini-Lesson
Mini-Lesson
We have learned to solve elapsed time problems using clocks and two-column tables.
Today, we will continue solving problems involving elapsed time to the nearest minute, where the end time and elapsed time are given, but the start time is unknown.
Listen as I think aloud...
Aran’s family went to dinner and then a movie. They took 46 minutes to eat dinner, and the movie lasted two hours and 30 minutes. If they finished and headed home by 9:00 PM, what time did Aran’s family start eating dinner?
In this problem scenario, we are trying to figure out when Aran’s family started eating dinner.
We know from reading the problem that Aran’s family ate dinner for 46 minutes and watched a movie for 2 hours and 30 minutes. Let’s use an open number line to find when Aran’s family began eating dinner.
An open number line is a great tool for solving elapsed time problems.
Watch as I draw an open number line and write down the ending time from the problem scenario. If we know it took Aran’s family 46 minutes to eat dinner and 2 hours and 30 minutes to watch a movie, we can figure out the beginning or starting time for these activities.
I know the family ended their activities at 9:00 PM. Let’s place 9:00 PM on the open number line. Nine o’clock will be at the far end of the number line on the right side because it is when dinner and a movie both end.
Since we are trying to determine the start time, we will count back the hours and minutes Aran’s family ate dinner and watched the movie on the number line.
First, count back 2 hours and 30 minutes from 9:00 PM to determine when the movie started.
We can jump back on the number line for 2 hours and then 30 minutes.
One hour before 9:00 PM is 8:00 PM. Another hour earlier from 8:00 PM is 7:00 PM.
Thirty minutes before 7:00 PM is 6:30 PM.
Two hours and 30 minutes before 9:00 PM is 6:30 PM. Aran’s family watched the movie at 6:30 PM.
Now, let us count 46 minutes from 6:30 PM to determine when Aran’s family started eating dinner.
I can decompose 46 minutes into 30 minutes and 16 minutes.
30 + 16 = 46
We can jump back on the number line 30 minutes from 6:30 to 6:00 PM.
Now, let’s jump back to the final 16 minutes. We can decompose 16 minutes as 10 minutes and 6 minutes.
30 + 10 + 6 = 46
Go back 6 more minutes from 5:50 PM to end at 5:44 PM.
Aran’s family began or started eating dinner at 5:44 PM. The unknown start time is 5:44 PM.
This makes sense. When I count on 46 minutes for dinner from 5:44 PM, the time will be 6:30 PM.
When I count on 2 hours and 30 minutes for the movie from 6:30 PM, the ending time will be 9:00 PM.
A t-chart strategy could also be used to subtract, rather than add, the elapsed time to find the start time.
See this example:
Guided Practice
Guided Practice
Now, mathematicians, it’s your turn - Solve this problem with a math partner:
Nadia read her book for one and a half hours and then played video games for 2 hours and 17 minutes. If Nadia finished reading her book and playing video games at 7:30 PM, what time did she begin?
Open number lines and two-column tables are great tools for organizing your math thinking when solving problems involving elapsed time. Remember to subtract the elapsed time from the ending time to figure out the starting time.
Practice in small groups - Complete BEFORE your rotation:
Solve, select, and write A, B, C, or D on the front of a sticky note.
Show your work on the back of the sticky note.
Maeve is baking cookies! She measured and blended the ingredients in the recipe for 26 minutes. Each batch of cookies needs to bake for exactly 13 minutes. If Maeve makes 3 batches of cookies and finishes baking all of them at 2:10 PM, what time did she start making the cookies?
a. 1:05 PM
b. 1:31 PM
c. 1:57 PM
d. 2:49 PM
Independent Task
Independent Task
1. FRECKLE - Complete THREE Freckle Assignments each week. DUE FRIDAY. Your HIGHEST score in Targeted Practice is your weekly math grade - Click HERE for Freckle website
GRADED Targeted Practice - Current skill (5 questions; Score Goal=80% or higher)
Fact Practice - Multiplication Fact Practice
Adaptive Practice - At YOUR level
2. iREADY Math - Complete 30 minutes at your level each week
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