Clock Face Showing 12:45

Topic

Time Measurement

Description

This image shows a clock face at 12:45, with the minute hand on the 9 and the hour hand three-quarters of the way to 1. This visual is excellent for teaching the concept of quarter-hour intervals.

Teachers can use this image to explain how the clock is divided into quarters and how each quarter represents 15 minutes. This understanding is crucial for students learning to read clocks accurately.

Math clip art like this is important for teaching time because it provides clear, visual examples that help students grasp the concept of time intervals. It supports the development of time-telling skills in a way that is both engaging and educational.

Teacher's Script: "This clock shows 12:45. The minute hand is on the 9, indicating a quarter to one. Notice how the hour hand is moving closer to 1. Let's explore other quarter-hour times using this clock."

For a complete collection of math clip art related to Telling Time click on this link: Clock Face Collection.

Video: Telling Time

To review telling time, watch this video. (The transcript is also included.)

The Hour Hand

When you look at a clock, you can read the hour and the minutes. Here is a blank clock face. Look at the arrangement of numbers on the clock face. Make a note of the following items:

• The numbers go from 1 to 12.
• There are additional tic marks between the main numbers.

Let’s start by looking at the hour hand. It is the shorter of the two clock hands and looks like this.

The hour hand varies in value from 1 to 12. Here are some sample times using the hour hand.

The Minute Hand

The minute hand is the longer of the two clock hands. This is what it looks like.

The minute hand varies in value from 0 to 60. Here are some sample times using the minute hand.

Why Are Hours Measured From 1-12 Not 1-10?

We are so accustomed to counting objects from 1-10 and in multiples of 10. Why are minutes and hours different? Why are minutes counted from 1 to 60? Why are hours counted from 1 to 12?

When we count from 1 to 10, we are using the base 10 system. The numbers cycle through groups of 10. But with clocks there is a different number system at work. Can you tell what the base is?

Clocks rely on a base 60 system. Think of the minute hand. After 60 minutes, the clock advances one hour and the minutes start again. This is an example of counting in base 60.

Why 60? With time measurement, we want to keep precise track of the time. The number 60 has many more factors, so we can measure time in fractions of 60 that are numbers that can be easily be remembered. Using base 10 with clocks would result in awkward fractions of time.

This table shows the fractions of an hour that result in whole number minutes of time that are easy to remember.

With base 60, there are so many more fractional amounts of time that are whole numbers, and they're easy to remember. Try this with base 10 and you won't end up with as many, easy-to-remember fractions.