Presentation on theme: "The 24-hour clock 1 12-hour clock 24-hour clock"— Presentation transcript:
1 The 24-hour clock 1 12-hour clock 24-hour clock The hours go from 12 to 12 twice a dayYou must use am or pm:am is before noonpm is after noon24-hour clockThe hours go from 0 to 23Time is always shown as four digitsYou don’t use am or pmUsed in timetables, mobiles and computers
2 The 24-hour clock 2After 12 o’clock in the afternoon, the hours continue to = 1pm,14.00 = 2pm, = 3pm, up to = 11pm.After 23, the hour goes to = 12am then through = 1am,02.00 = 2am all the way to = 11pm then again.Because all the hours have a different number, there is no needto use am or pm.For example there are two 4 o’clocks in a day:one in the morning 4:00 am = 04:00one in the afternoon 4:00 pm = 16:00An easy way to change to 24-hour time is to add 12 onto thehour. You only do this to the hours between 1pm and 11pm.Midnight becomes 00:00.
3 The 24-hour clock 3Fill in the 24-hour times on the scale below on your worksheet.12-hour timeampm00.0024-hour time
4 The 24-hour clock 4When converting to 24-hour time you change the hours only.12 hour 24 hour3.00am 03:008.15am 08:1511.45am 11:452.35pm 14:355.20pm 17:2011.38pm 23:3812.55am 00:55Notice that you only add 12 onto the pm times.
5 The 24-hour clock 5Change the following times from 12 hour into 24 hour.5am8am2.45am12.02am11.38am12.01pm1.29pm7pm10.45pm11.07pm05:0008:0002:4500:0211:3812:0113:2919:0022:4523:07Now check your answers.
6 The 24-hour clock 6To convert from 24 hour to 12 hour you do the opposite.Take away 12 from the hours if it is 13 to 23.Midnight changes from 00:00 to 12:00am.Change the following times from 24 hour into 12 hour.4am7am9.45am12.20am11.02am12.56pm4.22pm8.20pm9.21pm10.18pm04:0007:0009:4500:2011:0212:5616:2220:2021:2122:18Now check your answers.
7 Time intervals 1To calculate time intervals, you need to count forward.You might want to calculate time intervals for a variety ofreasons.You might want to know how long a film lasts, how long a journeyis going to last, how long you are in each class for in school.Can you think of any other reasons why you might want tocalculate a time interval?To calculate the interval between 4.00am and 7.00am you countForward.Start at 4 and count forward to 7 = 3 hours.1+ 1+ 14567
8 Time intervals 2Find out how long there is between each of these times5.00pm and 8.00pm11.00pm and 4.00am3.30pm and 6.30pm22:40 and 00:4007:05 and 12:0512:55 and 14:557.
9 Time intervals 3Find out how long there is between each of these times3.15pm and 5.15pm9.05pm and 2.05am7.15pm and 10.15pm14:10 and 23:1017:25 and 22:2513:05 and 18:057.
10 Time intervals 4To find out how many minutes there are between two time intervalsand the times are in the same hour, take away the minutes.For example:4.05 to 4.4545 – 5 = 40 minutesThe times are in the same hour, 4.This means that you can take away the minutes to calculate thetime interval.6.20 to 6.55= 35 minutes14:05 to 14:2525 – 5 = 25 minutes
11 Time intervals 5Find out how long there is between each of these times:5.05pm and 5.20pm11.00pm and 11.45pm3.30pm and 3.55pm22:40 and 22:5507:05 and 07:4512:45 and 12:557.
12 Time intervals 6Calculating time intervals in minutes from one hour to the nextcan be broken down into two steps.Step 1 Count the minutes to the next hourStep 2 Add on the minutes to the finish timeHow long is it in minutes between:3.50 pm and 4.25 pmStep minutes till 4 o’clockStep – 4.25 = 25 minutes10+2535 minutesHow long is it in minutes between6.25 pm and 7.15 pmStep minutes till 7 o’clockStep – 7.15 = 15 minutes35+1550 minutes
13 Time intervals 7Find out how long there is between each of these times:5.55pm and 6.20pm11.35pm and 12.20pm3.30pm and 4.05pm22:40 and 23:1507:10 and 08:0512:45 and 13:357.
14 Time intervals 8 Remember that there are 60 minutes in an hour. If the time interval adds up to more than 60 minutes, change itinto hours and minutes.How long is it in minutes between:3.40 pm and 4.55 pmStep minutes till 4 o’clockStep – 4.55 = 55 minutes20+5575 minutes75 minutes = 1 hour (60 minutes) and 15 minutesHow long is it in minutes between:6.25 pm and 7.45 pmStep minutes till 7 o’clockStep – 7.45 = 45 minutes35+ 4580 minutes80 minutes = 1 hour (60 minutes) and 20 minutes
15 Time intervals 9Find out how long there is between each of these times:5.50pm and 6.55pm11.35pm and 12.50pm3.30pm and 4.45pm22:40 and 23:5507:10 and 08:4512:45 and 13:557.
16 Time intervals 10To calculate time intervals between hours follow these steps.4.15 pm to 7.25 pm.45 minutes+ 2 hours+ 25 minutes4.15 pm to 5.00 pm5.00 pm to 7.00 pm7.00 pm to 7.25 pm45+ 2570 minutes70 minutes = 1 hour (60 minutes) and 10 minutes+ 2 hours = 3 hours 10 minutes19.20 pm to pm.40 minutes+ 1 hour+ 55 minutesto 20.0020.00 to21.00 to40+ 5595 minutes95 minutes = 1 hour (60 minutes) and 35 minutes+ 1 hour = 2 hours 35 minutes
17 Time intervals 11Find out how long there is between each of these times:5.50pm and 8.55pm11.35pm and 6.50pm3.30pm and 12.45pm22:40 and 00:5507:10 and 12:4512:45 and 20:557.
18 Time intervals 12It is also very useful to be able to calculate time intervals in days,weeks and months.You may want to know how long it is until your birthday, or how longit is until your holidays or Christmas.Can you think of any other reasons why you might want tocalculate time intervals using a calendar?
19 Calendars 1AugustMondayTuesdayWednesdayThursdayFridaySaturdaySunday31123456789101112131415161718192021222324252627282930You can calculate how many weeks and days there are betweentwo dates by counting down the column.How many weeks is it between the 5th and the 26th?= 3 weeksHow many weeks and days is it between the 5th and the 30th?= 3 weeks and 4 days
20 Calendars 2JanuaryMondayTuesdayWednesdayThursdayFridaySaturdaySunday123456789101112131415161718192021222324252627282930311. How long is it between January 7th and 21st?2. How long is it between January 1st and 29th?3. How long is it between January 13th and 27th?4. How long is it between January 19th and 26th?5. How long is it between January 21st and 28th?
21 Calendars 3AprilMondayTuesdayWednesdayThursdayFridaySaturdaySunday1234567891011121314151617181920212223242526272829301. How long is it between April 1st and 23rd?2. How long is it between April 1st and 9th?3. How long is it between April 4th and 27th?4. How long is it between April 7th and 30th?5. How long is it between April 10st and 22nd?
22 Time intervals between months 1 January February MondayTuesdayWednesdayThursdayFridaySaturdaySunday12345678910111213141516171819202122232425262728293031FebruaryMondayTuesdayWednesdayThursdayFridaySaturdaySunday12345678910111213141516171819202122232425262728How long is it between January 15th and February 12th?4 weeks (you don’t include the 15th)How long is it between January 15th and February 14th?4 weeks and 2 days
23 Time intervals between months 2 January February TueWedThuFriSatSun12345678910111213141516171819202122232425262728293031FebruaryMonTueWedThuFriSatSun12345678910111213141516171819202122232425262728How long is it between the following dates:1. January 1st and February 23rd?3. January 28th and February 13th?2. January 21st and February 28th?4. January 31st and February 28th?
24 Time intervals between months 3 January February TueWedThuFriSatSun12345678910111213141516171819202122232425262728293031FebruaryMonTueWedThuFriSatSun12345678910111213141516171819202122232425262728How long is it between the following dates:1. January 11th and February 4th?3. January 18th and February 27th?2. January 26th and February 19th?4. January 27th and February 24th?
25 Time intervals between months 4 January February TueWedThuFriSatSun12345678910111213141516171819202122232425262728293031FebruaryMonTueWedThuFriSatSun12345678910111213141516171819202122232425262728How long is it between the following dates:1. January 4th and February 1st?3. January 15th and February 23rd?2. January 13th and February 2nd?4. January 18th and February 1st?