Reading clocks and adding time

A clock with hands is called an analogue clock. Many people now read the time from a phone, but clocks with hands are still on walls, towers, ovens and watches everywhere, and they let you see at a glance how much of the hour has gone and how much is left. Adding time is a different skill. An hour has 60 minutes, not 100, so time does not add like ordinary numbers. Both skills are easy once you know the method.

The two hands

A clock has two hands. The short hand shows the hour. The long hand shows the minutes. The numbers 1 to 12 go around the face, and between every two numbers there are small marks for the minutes. On many clocks only 12, 3, 6 and 9 are written, and the other numbers are just marks. They are still in the same places, so you can count them from 12.

Reading the minutes

The long hand goes all the way round in one hour, which is 60 minutes. There are 12 numbers, so each number is worth 60 ÷ 12 = 5 minutes. When the long hand points to a number, multiply that number by 5.

Reading the hour

The short hand moves slowly. It takes a whole hour to go from one number to the next. So most of the time it is between two numbers. The hour is the number it has just passed, which is the smaller of the two. The only special case is between 12 and 1: there the hour is 12.

You can check your answer with the short hand too. At half past, it is halfway between two numbers. At 40 minutes past, it is two thirds of the way to the next number, so it is close to the next number but has not reached it.

1. Look at the long hand. Multiply the number it points to by 5. That gives the minutes.
2. Look at the short hand. Take the number it has just passed. That is the hour.
3. Write the hour, a colon, then the minutes with two digits: 8:05, not 8:5.

Adding minutes to a time

When the minutes go past 60, a new hour starts. The clearest way to add time is to stop at the next o'clock first. Fill up the hour, then add what is left.

1. Find how many minutes are left until the next o'clock: 60 minus the minutes now.
2. Move to that o'clock and take those minutes away from the time you are adding.
3. Add the minutes that are left after the o'clock.

On a clock with hands, the hours go up to 12 and then start again. One hour after 12:20 is 1:20, not 13:20. A 24-hour clock, used on timetables, keeps counting: there 1:20 in the afternoon is 13:20.

How long does something last?

You can turn the method round to find how long something takes. Count up from the start time: first to the next o'clock, then on to the end time, and add the pieces.