Te Kete Ipurangi
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# Clock Wise

Keywords:
Purpose:

In this unit students explore hours and half-hours and experiment with two ways of telling these times, using digital and analogue approaches.

Achievement Objectives:

Achievement Objective: GM2-1: Create and use appropriate units and devices to measure length, area, volume and capacity, weight (mass), turn (angle), temperature, and time.
AO elaboration and other teaching resources

Specific Learning Outcomes:
• tell time to the hour and half hour using analogue clocks
• tell time to the hour and half hour using digital clocks
• solve time problems involving hours and half hours
Description of mathematics:

This unit introduces time telling, using the two common forms of clocks – analogue and digital. There is a concentration here on hour times and half hour times and the fact that there are 60 minutes to an hour. Clearly time is an important issue in our lives and in mathematics. This unit provides an introduction to reading, telling and understanding the time.

Required Resource Materials:
thin card (to make clock face and hands)
split pins
analogue clock(s) (without a second hand and with the facility to change the time easily)
digital alarm clock(s)
Activity:

#### Getting Started

1. Begin by brainstorming the words we use to talk about time and listing these. For example, 20 past/to, quarter or half past/to, o’clock, four fifty, hours, minutes and seconds.
2. Explain to the students that there are several different ways to describe time and this week they are going to explore two of these.
3. Show an analogue clock and discuss the face, drawing out the students' experiences with clocks and time.
What can you tell me about the face?
What numbers are there? Why (is there nothing above 12)?
How are the numbers arranged? Why?
Tell me about the clocks that you have at home?
What is the biggest clock you have ever seen?
When do you get up?
When do you go to school?
4. Have each student construct an analogue clock:
Draw around an object to make a circle of light card or give each student a cut circle of card.
Fold the circle in half and colour each half a different colour – this helps reinforce the concept of half.
Make a big and a small hand and attach these with a split pin.
Draw numbers onto the clock-face.

#### Exploring

Analogue Time

1. As a group, discuss times of the day when well known events happen and have the students model these times on the analogue clocks they have made. At first focus on hours, e.g. school starts at nine o’clock; eight o’clock is bedtime. Then move on to half-hours, e.g. half past ten is playtime.
2. As students work at modelling times, focus on the position of the hands (big hand shows minutes and little hand shows hours) and the terms half past and o’clock.
3. Students can record some of their favourite times of the day and draw clocks showing those times.

Analogue Time Problems
Pose several problems involving time (to hours and half-hours). Place these problems on cards stationed around the room and have the students work with a buddy and their analogue clock to solve them and record their answers. As a group, discuss the problems and their solutions.

Possible problems include:

• Sally went swimming at 4 o’clock and got out of the pool at half past five. How long did she swim for?
• If it takes half an hour to walk to school from home, how long will it take to walk to school and back home again?
• Laura had an appointment at the dentist at half past three. She didn’t arrive until 4 o’clock. How late was she?
• The movie started at 6 o’clock and finished at half past seven. What was the running time of the movie?
• Mark went to bed at 8 o’clock and woke up 11 hours later. What time did he wake up?
• Muffins take half an hour to cook. If a batch of muffins goes into the oven at half past five what time will they be ready?

Digital Time

1. Have the students carefully examine a digital clock and count the number of minutes in each hour. Establish that there are 60 minutes in each hour, and therefore 30 minutes in half an hour. This is also a good opportunity to practice skip-counting with fives.
2. Establish with the students that the first number of the digital clock shows the hour and the second number shows the number of minutes past that hour.
3. Challenge the students by asking them how they think the digital clock would show times that they are familiar with on an analogue clock e.g. nine o’clock (start of school), and half past ten (play time).
4. Reinforce the fact that half an hour is thirty minutes, therefore digital times ending in 00 are the same as o’clock and times ending in 30 are the same as half past.
5. List some of the students’ favourite TV programmes and have the students record the digital times these programmes come on. Look at a TV guide to confirm the times that they have recorded.

Digital Time Problems

Pose several problems involving time (to hours and half-hours). Place these problems on cards stationed around the room and have the students work with a buddy to solve them and record their answers. As a group, discuss the problems and their solutions.

Possible problems include:

• Sally went to play netball at 4.00 and came home at 5.30. How long was she away?
• If it takes 30 minutes to walk to the beach from home, how long will it take to walk to the beach and back home again?
• Laura had an appointment at the doctor at 2.30. She didn’t arrive until 3.00. How late was she?
• Hine’s TV programme started at 7.00 and finished at 8.30. How long was the programme?
• Mark went to his grandma’s at 2.00 and stayed there for 6 hours. What time did he leave?
• Potatoes take 30 minutes to boil. If Mum wants the potatoes to be ready by 5.30, when must she put them in the boiling water?

Mixed Time

1. Divide the class into two groups. One of these is the analogue group and the other the digital group. Give each group an appropriate clock,
2. Let the analogue group choose a time (involving hours or half-hours). Get the digital group to show that time on their clock.
3. Then let the digital group choose a time and ask the analogue group to show it on their clock. Repeat this a few times.
4. Choose any time. Ask questions like
Show me the time in half an hour?
What will be the time 3 hours from now?
What was the time 30 minutes ago?
What will be the time in 60 minutes?
What was the time three half hours ago?
5. Get the groups to make up their own problems like this and like the ones we used earlier. Allow the students to ask each other the questions. Get the students to draw their answers using drawings of both an analogue clock and a digital clock.
6. Ask the students to tell you the main times of the day (when school starts, play time, lunchtime, etc.). Get them to draw these in both analogue and digital formats. Put a selection of their drawings on the wall to refer to later.

#### Sharing

Over the course of one day have each student keep a record of what they are doing on the hour and at half past the hour. To help you remember, set a digital alarm clock to go off every half-hour, getting the students to help with this. Have students record what they are doing along with the analogue time in a diary.

Compare the differences and similarities in the students’ diaries.

Pose the following questions for discussion during the day.

Why is the term ‘half past’ used to tell the time?
In the term ‘half past’, what does the word ‘half’ refer to?
What are the units of time?
What is the relationship between minutes and hours?