Transcript Digital/ Analog Time

Digital/ Analog Time
4th Strategies for Your Toolbox in
Solving Problems Involving Digital/
Analog Time
Vocabulary
• Digital clock: instrument that reads time
in a numerical format
• Analog clock: time represented by hands
on a dial
Digital Clocks
• When reading a digital clock,
– the 1st number to the left of the colon is
the hour
1st number
2nd number
5 hours and 8 minutes
– the 2nd number to the right of the colon is
the minutes
Analog Clocks
• Reading an analog clock:
– short hand represents the hour
– long hand represents minutes
•hour = short word = short hand
•minutes = long word = long hand
– count by 5s to find total minutes if
minute hand is on a number 1-12,
otherwise count by 1s
Counting
by 5s
55
60
5
10
50
45
15
40
20
35
25
30
Toolbox Strategies for Reading/
Matching Digital & Analog Time
• 1st number on a digital clock always
matches number the short hand is on
– if the short hand is between 2 numbers, the
hour is the lesser of the 2 numbers
Count Us In Games - Game 10
Aplusmath.com : Flashcards : Analog Clocks
Elapsed Time
Elapsed time – time that has passed
Ex: If I say that the party lasted from 5:30 PM
to 7:30 PM, then 2 hours passed, or
elapsed.
It can be measured in:
seconds
Picturing or using
minutes
a clock
hours
will help
days
weeks
Types of Elapsed Time Problems
1. You know when an event started and
when it ended. You have to find the
amount of time that has passed.
Ex: The TV program started at 8:30 PM
and ended at 9:00 PM. How many minutes
did the program last?
Types of Elapsed Time Problems
Ex: The TV program started at 6:30 PM &
ended at 7:00 PM. How many minutes did
the program last?
To calculate the total
minutes
– Picture a clock showing
6:30
– Count by 5s until you
reach 7:00
Types of Elapsed Time Problems
Ex: The TV program started at 6:30 PM &
ended at 7:00 PM. How many minutes did
the program last?
To calculate the total minutes
– Picture a clock showing
6:30
– Count by 5s until you
reach 7:00
* Notice that the clock now
shows 7:00
Types of Elapsed Time Problems
Ex: The TV program started at 6:30 PM &
ended at 7:00 PM. How many minutes did
the program last?
To calculate the total
minutes (strategy 2)
– Since the question asks
about minutes, subtract
them (30 min – 00 min =
30 min)
- Answer: 30 minutes
Types of Elapsed Time Problems
2. You know when an event started and
how long it will last. You have to find
when the event will end.
Ex: The TV program started at 1:30 PM
and lasted for 30 minutes. When did the
program end?
Types of Elapsed Time Problems
Ex: The TV program started at 1:30 PM
and lasted for 30 minutes. When did the
program end?
To calculate the program end time
• You’re told how long the program
lasted in minutes. Add the minutes from the
start time to the minutes of how long the
program lasted. (30 min + 30 min = 60 min)
Types of Elapsed Time Problems
Ex: The TV program started at 1:30 PM and
lasted for 30 minutes. When did the program
end?
To calculate the program end time
• When working with units of measurement, it’s
best to use easy numbers so whenever possible
convert to a unit that reduces a bigger number.
• 60 minutes is equal to 1 hour so add the hours:
1hour from the start time to 1 hour from the
minutes added together (1 hr + 1 hr = 2 hrs)
• Answer: 2:00 PM
Types of Elapsed Time Problems
3. You know when the even will end, and
how long it will last so you have to find
when the event will begin.
• Ex: The TV program lasted for 30 minutes
and ended at 2:00. When did the program
start?
Types of Elapsed Time Problems
• Ex: The TV program lasted for 30 minutes
and ended at 2:00 PM. When did the
program start?
To calculate the start time
• There are 2 hours to work with since the
program ended at 2:00.
• 60 minutes equal 1 hour, so subtract 30
minutes from 60 minutes (60 min – 30 min =
30 min)
•The time that’s left is 1 hour and 30 minutes
• Answer: 1:30 PM
Elapsed Time
Let’s practice
some elapsed
time problem!!
mathFROG - Fun Resources &
Online Games
Elapsed Time Practice
How much time has gone by between the times
on the first and second clocks?
15 minutes
Elapsed Time Practice
How much time has gone by between the
times on the first and second clocks?
55 minutes
Elapsed Time Practice
Maureen started her homework at 7.20 p.m.
She finished it at 8.05 p.m. How long did she
take to do her homework?
50 minutes
Toolbox Checklist for Solving
Elapsed Time Problems
 Analog clock (You can make, draw, or use
one that your teacher may provide.)
 Knowledge to remember: hour hand = short
word = short hand; minute hand = long word
= long hand
 Manipulate the hands to show times
Knowledge to remember: 60 seconds = 1
minute; 60 minutes = 1 hour
 Count by 5s
Questions???