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7/29/2019 Time Units
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1 year = 365 days
1 year = 52 weeks1 year = 12 months
1 week = 7 days
1 day = 24 hours1 hour = 60 minutes
1 minute = 60 seconds
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a.m. or A.M. an abbreviation
of ante meridiem (before noon)
p.m. or P.M.
an abbreviation ofpost meridiem (after noon)
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International Date Line
an imaginary line through the
Pacific Ocean roughly along the180th meridian, agreed upon as the
place where each new calendarday begins. The calendar day to
the east of the line is one day
earlier than to the west.
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prime meridian The zero
meridian (0) used as areference line from which
longitude east and west is
measured. It passes through
Greenwich, England.
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Time Conversion
Using a bridge map can
help organize your thinking
when converting from one
time unit to another.
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as(just like)
Relating factor
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Example:4 weeks = ______ days28
Think: 1 week = 7 days
4 x 7 = 281 week
7 days
4 weeks
days28
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Example:
3 years = ______ months
3 x 12 = 36
36
Think: 1 year = 12 months
1 year
12 months
3 years
months36
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Example:
3 days 8 hours = ______ hours
3 x 24 = 72 + 8 = 80
80
Think: 1 day = 24 hours
1 day
24 hours
3 days 8 hours
hours80
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Example:
420 seconds = ______ minutes
420 60 = 7
7
Think: 60 seconds = 1 minute
60 seconds
1 minute
420 seconds
minutes7
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Example:
42 months = __ years __ months
Think: 12 months = 1 year
42 12 = 3 r 6
3 6
12 months
1 year
42 months
__ years __months3 6
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Example:
100 hours = _____ days
Think: 24 hours = 1 day
100 24 = 4 4/24 = 4 1/6
4 1/6
24 hours
1 day
100 hours
___ days4 1/6
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Time units can be added,
subtracted, multiplied or divided.
To add or subtract measures of time:
1. Add or subtract the seconds.
2. Add or subtract the minutes.3. Add or subtract the hours.
Rename if necessary in each step.
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Find the sum.
15 h 23 min
+ 7 h 15 min
Add minutes
38 min
Add hours
22 h
Rename answerif necessary
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Find the sum.
6 h 12 min
+ 1 h 55 min
Add minutes
67 min
Add hours
7 h
Rename answerif necessary
= 8 h 7 min
67 min = 1 h 7 min
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Find the difference.
5 h 48 min
- 2 h 12 min
36 min
Subtract hours
3 h
Subtract minutes
Rename answerif necessary
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Find the difference.
24 min
- 13 min 12 s
Subtract minutes
10 min
Subtract seconds
Rename answerif necessary
23
60 s
48 s
5 10
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Ending Time
- Starting Time
Elapsed Time
To calculate elapsed time
subtract the starting time from
the ending time of the event.
9:55 a.m.
- 6:35 a.m.
3 h 20 min
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10:50
- 7:30
Subtract minutes
20hr
Subtract hours
33 hours 20 minutes
Start timeEnding time
Marcy was babysitting from
7:30 p.m. to 10:50 p.m. How
long did Marcy baby-sit?
min
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Military time is based
on a 24 hour clock.
24
hour
clock
Hours from 1:00 a.m. to 12:00 p.m
are from 01:00 to 12:00Hours from 1:00 p.m. to 12:00 a.m.
are from 13:00 to 24:00
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Add 12 hours to 1: 00 p.m.
to 12:00 a.m. to change from
standard time to military time.Examples:
1:15 p.m. is 13:15 military time9:45 p.m. is 21:45 military time
12:00 a.m. is 24:00 military time
1:30 a.m. is 01:30 military time
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11:30
- 6:5040hr4
Susie worked from 6:50 a.m. to
11:30 a.m. on Monday. How
long did she work?10 90
Subtract hoursSubtract minutes
Rename 1 hour to minutes
4 hours 40 minutes
min
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8:25
- 1:4540hr
John worked from 1:45 p.m. to
8:25 p.m. on Wednesday. How
long did he work?7 85
Subtract hoursSubtract minutes
Rename 1 hour to minutes
6 hours 40 minutes
6 min
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6:00
- 10:3030hr7
Think:military
time
add 12
to hour
John worked from 10:30 a.m.to 6:00 p.m. on Friday. How
long did he work?Add 12 to hour
7 hours 30 minutes
18:0017 60
Rename 1 hour to minutes
Subtract hoursSubtract minutes
min
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Time units can be expressed
using fractions..
Quarter of an hour
Half an hour
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