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Lesson · Grade 4 · Mathematics

3:15 p.m. or 15:15? Morning, afternoon and the 24-hour clock

  • Grade 4
  • Mathematics
  • 1 min 12 s
  • British Columbia
  • BC4-MA-22

A clock showing 3:15 turns through one whole day on a bar from midnight to midnight, so children see 3:15 come once in the night (a.m.) and again 12 hours later in the afternoon (p.m.). Then the 24-hour clock keeps counting after noon, 13, 14, 15, checked by 12 + 3 = 15 with the minutes unchanged, showing that 3:15 p.m. and 15:15 are the same time (and 3:15 a.m. is 03:15).

Concept: Morning or afternoon: a.m., p.m. and the 24-hour clock

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In one sentence

The question this lesson answers

Is it 3:15 at night, or in the afternoon?

A day has 24 hours, but a clock face shows only 12.

Transcript

What the lesson says

Is it 3:15 at night, or in the afternoon?

A day has 24 hours, but a clock face shows only 12.

From midnight, 3:15 comes first in the night.

12 hours later, 3:15 comes again in the afternoon.

Times after midnight and before noon are a.m.

Times after noon and before midnight are p.m.

Now let us write 3:15 p.m. on the 24-hour clock.

After 12 noon, the 24-hour clock keeps counting.

1 p.m. is 13, 2 p.m. is 14, and 3 p.m. is 15.

Check it: 12 plus 3 is 15.

The minutes stay the same, so 3:15 p.m. is 15:15.

And 3:15 a.m. is written 03:15.

3:15 p.m. and 15:15 are the same time of day.

Curriculum

Where this fits

British Columbia, Grade 4

Mathematics, Geometry and measurement: how to tell time with analog and digital clocks, using 12- and 24-hour clocksBC4-MA-22

Previous: Reading an Analog Clock to the Nearest MinuteNext: Regular and Irregular Polygons

The outcomes and strands follow the British Columbia curriculum.

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