24-hour clock and timetables

Hello, and welcome to Myriora Maths! On a train timetable, a train leaves at fourteen thirty-five. What time is that? Timetables use the twenty-four hour clock. Let's learn how it works.

The twenty-four hour clock counts the hours of the whole day, from nought to twenty-four. In the morning, the hours are the same: nine a m is nine hundred hours. After midday, add twelve. Three p m is fifteen hundred, and seven forty-five p m is nineteen forty-five.

Midnight is nought nought hundred: the start of a new day. And midday is twelve hundred.

Here's a bus timetable. The bus leaves the station at fourteen thirty-five, and gets to the park at fifteen ten. How long is the journey?

Count on, using the next o'clock. From fourteen thirty-five to fifteen hundred is twenty-five minutes. Then on to fifteen ten is ten more minutes. Twenty-five add ten is thirty-five minutes.

Let's try one together. What is seven forty-five p m in the twenty-four hour clock? Say it out loud!

After midday, add twelve. Seven add twelve is nineteen. So it's nineteen forty-five!

Here's a question that catches lots of people. How long is it from fourteen fifty to fifteen twenty? Some people take the numbers away like ordinary numbers: fifteen twenty take away fourteen fifty is seventy. But an hour has sixty minutes, not a hundred! Count on: ten minutes to fifteen hundred, then twenty more. Thirty minutes.

Your turn! A train leaves at nine forty, and arrives at eleven fifteen. How long is the journey? Pick the right card. You've got twenty seconds, or pause the video. Go!

Time's up! Nine forty to ten o'clock is twenty minutes. Ten to eleven is one hour. Eleven to eleven fifteen is fifteen minutes. That's one hour and thirty-five minutes!

Quick review. The twenty-four hour clock counts the whole day. After midday, add twelve to the hour. Midnight is nought nought hundred. To find how long something takes, count on through the o'clocks, because an hour is sixty minutes. See you next time!