Time Units

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


= 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



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Find the difference.

24 min

- 13 min 12 s

Subtract minutes

10 min

Subtract seconds


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



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



min


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Time units can be expressed

using fractions..

Quarter of an hour

Half an hour

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Time Units