TIME By the end of the lesson I

TIME

By the end of the lesson I will be able to… • Express and calculate time using 12 and 24 hr timings • Know and understand time is measured and calculated in base 60 not base 10 • Understand use fractional time and minute/ hour equivalences

What time is it? 4: 10 How do we know if it is daytime or night time? 5: 35 9: 40 12: 35 6: 05 5: 10 4: 45 11: 15 3: 30 Time to do some work – Miss!

When using the 12 -hour clock we can use: AM 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 PM

We don’t use AM or PM in 24 hour clock! • • • 1 am 2 am 3 am 4 am 5 am 6 am 7 am 8 am 9 am 10 am 11 am 12 noon • • • 01: 00 02: 00 03: 00 04: 00 05: 00 06: 00 07: 00 08: 00 09: 00 10: 00 11: 00 12: 00

For PM times we keep counting to 24! • • • 1 pm 2 pm 3 pm 4 pm 5 pm 6 pm 7 pm 8 pm 9 pm 10 pm 11 pm 12 midnight • • • 13: 00 14: 00 15: 00 16: 00 17: 00 18: 00 19: 00 20: 00 21: 00 22: 00 23: 00 24: 00 / 00: 00

Look at Midnight! • 12: 00 midnight • 00: 00 • Why? ? ?

• Why 24 hours? • The 24 -hour day concept comes from the ancient Egyptians. • They divided the day into 10 hours with devices like shadow clocks • They then added one hour at each end (one for twilight and one at the end of the day). • Later, a T-shaped bar was made by Egyptians, which was calibrated to divide the time between sunrise and sunset into 12 parts. • However, the absence of sunlight made it difficult to divide the time at night. It’s pretty interesting to learn how they managed to do this. Yes, night time division of time was based on the observation of stars! So, how can we work out the time from a 12 hour clock 24 hour clock? https: //www. youtube. com/watch? v=kd-Pg. DKz 0 N 0

What about the minutes? • In 24 hour time the minutes don’t change. • 1. 15 am 01: 15 • 2: 45 am 02: 45 • 6: 24 pm 18: 24 • 8: 30 pm 20: 30 • 10: 45 am 10: 45 • 11: 35 pm 23: 35

Noon & Midnight • Noon • 12: 00 pm • 12: 15 pm • 12: 30 pm • 12: 45 pm • 12: 50 pm • 12: 05 pm • 12: 10 pm 12: 00 12: 15 12: 30 12: 45 12: 50 12: 05 12: 10 • Midnight • 12: 00 am • 12: 15 am • 12: 30 am • 12: 45 am • 12: 50 am • 12: 05 am • 12: 10 am 00: 00 00: 15 00: 30 00: 45 00: 50 00: 05 00: 10

Answer the questions on the sheet, by recording the time on the clock for that country.