Telling time to the half hour - math grade 2 - lesson 57

Yesterday we used our clocks to show time to the hour. Th e minute hand stayed on the 12 and we moved only the hour hand to show the hour. In today’s lesson, we learn how to tell time to the half hour. It is important we understand that when the time is 4:30, the minute hand is halfway around the clock and that the hour hand is halfway between the 4 and the 5. we should also recognize that half an hour is 30 minutes (half of 60 minutes).

Note to the Teacher: Due to the nature of teaching children to tell time, there is a lot of teacher-talk in this lesson. Where possible, cut sections of the lesson that students do not need and extend sections when they need more practice. Be sure to check students’ levels of understanding and engagement as you move through the lesson.

1.TEACHER SAY: Yesterday we made our own analog clocks. Take out your clocks so we can use them.

STUDENTS DO: Take out the clock they made in Lesson 56.

TEACHER SAY: Let’s try that now. I am going to show a time on my clock. Once I am done, make your clock look the same, and when you know what time it is, give me a Thumbs Up.

TEACHER DO: Make a time on the clock that is exactly to the hour, like 4:00.

STUDENTS DO: Make 4:00 on their clock and then give a Thumbs Up. Selected students share their answer.

TEACHER SAY: Yes, the time is 4:00. The minute hand is on the 12 and the hour hand is pointing directly at the 4. We write that by writing the hour first and then the minutes.

TEACHER DO: Write 4:00 on the board. Then draw arrows and write the words “hour” and “minutes” as shown.

TEACHER SAY: So far, we have not moved the minute hand around, but it moves all the time. Every hour the minute hand goes one full time around the clock, while the hour hand just moves one more hour, or number. When the time changes from 4:00 to 5:00, this is what the hands will do.

TEACHER DO: Show 4:00 and then Model how the minute hand moves all the way around and the hour hand just moves to 5.

TEACHER SAY: At 5:00, the minute hand is back at the 12 after making a full rotation around the clock. The hour hand has only moved from 4 to 5. There are 60 minutes in one hour. It takes 60 minutes for the minute hand to go all the way around. Let’s try that moving both hands. Start with your clock at 7:00.

STUDENTS DO: Move the hands on their clock to show 7:00.

TEACHER SAY: Now move your minute hand all the way around and back to the 12 and move the hour hand from the 7 to the 8. Note to the Teacher: This is a tricky concept since both hands move, but the hour hand moves much more slowly.

TEACHER DO: Model moving both hands to show the hour change.

STUDENTS DO: Move both hands to show the change from 7:00 to 8:00.

TEACHER SAY: Now it is 8:00. The minute hand traveled all the way around and the hour hand moved from the 7 to the 8. One hour has passed. Sometimes the minute hand points straight up at the 12. When that happens, we know that it is exactly an “o’clock” time, such as 8:00. It is an exact hour. But what if the minute and hour hands move and the clock looks like this?

TEACHER DO: Using your large clock, move the minute hand from the 12 to the 6 slowly, showing how the hand is moving halfway around the clock. Move the hour hand to between the 8 and the 9.

TEACHER SAY: What time do you think it is when the hour hand is between the 8 and 9 and the minute hand is at the 6? Turn and Talk to your Shoulder Partner. Share your thinking.

STUDENTS DO: Turn and Talk to Shoulder Partner and share their thinking about the time shown on the teacher’s clock.

TEACHER SAY: Remember when we folded our clocks in half? The fold went from the 12 to the 6. When the minute hand moves from the 12 to the 6, it has moved halfway around the clock. It has moved a half of an hour. Move your minute hand from the 12 to the 6.

STUDENTS DO: Move minute hand to the 6.

TEACHER SAY: This minute hand has moved halfway around the clock, from the 12 to the 6. The hour hand has also been moving. It has moved halfway between the 8 and the 9. The hour hand moves much more slowly than the minute hand. Move your hour hand to look like my clock. What hour do we think it is now?

STUDENTS DO: Move hour hand between the 8 and the 9.

TEACHER DO: Point to the hour hand.

TEACHER SAY: Raise your hand if you think the hour is still 8.

STUDENTS DO: Raise their hand if they think it is still 8.

TEACHER SAY: Raise your hand if you think the hour is 9.

STUDENTS DO: Raise their hand if they think it is 9.

TEACHER SAY: Good ideas. Some of you think 8 and some of you think 9. This can be a challenging part of telling time. The hour hand has passed 8 but has not yet arrived at 9. That means that our hour is still 8. This is like if I start on a number line and walk from 8 to 9. I am not at 9 until I get to the 9. With time, it is the same. We read the hour as the number that we are exactly at or passed until we get to the next number.

TEACHER DO: On the board draw a line as shown below. Using a finger, start at 8 and walk along the line until exactly at 9. Then stop.

TEACHER SAY: So the hour on our clock is 8, since we are not yet at 9.

TEACHER DO: Write the first half of the time on the board (with a colon): 8:.

TEACHER SAY: Now we have to figure out how to read the minute hand. Remember that earlier I told you there were 60 minutes in an hour? It takes the minute hand 60 minutes to go all the way around.

TEACHER DO: Draw a number line counting by 5s from 0 to 60. Be sure the lines are evenly spaced.

TEACHER SAY: Let’s look at this line. The numbers on the top are the numbers on the clock. The numbers on the bottom skip count by 5s from 0 to 60. We start at 0 because when the hour begins and the minute hand is exactly at 12, 0 minutes have passed. At the other end of the line is the number 60, because when a whole hour has passed and the minute hand gets back to the 12, 60 minutes have passed. Look at your clock. When it is folded in half, what number is at the bottom of the clock? Give me a Thumbs Up when you know.

STUDENTS DO: Look at their clock to see what number is in the fold. Give a Thumbs Up when ready. Selected students share their answers.

TEACHER SAY: Yes, the 6 is in the middle. When the minute hand is pointing at the 6, it has traveled halfway around the clock. It has been half an hour.

TEACHER DO: Point at the 6 on the number line.

TEACHER SAY: You count the numbers under the number line, while I count the numbers above the number line.

STUDENTS DO: Count by 5s from 0 to 30 as the teacher points to and counts from 0 to 6.

TEACHER SAY: So, 6 is halfway around the clock. 60 minutes is a whole hour. How many minutes is a half an hour (half of 60)?

STUDENTS DO: Call out: 30.

TEACHER DO: Circle 30.

TEACHER SAY: Yes, 30 is half of 60, so I have circled it. If the minute hand has traveled halfway around the clock, it has traveled 30 minutes. The hour hand is halfway between 8 and 9 and the minute hand has traveled halfway around the clock and is at the 6. The time is 8:30. Say that with me.

STUDENTS DO: Say 8:30 with the teacher.

TEACHER DO: Write the minutes on the board so the time reads 8:30.

TEACHER DO: Add labels to 8:30 as shown.

TEACHER SAY: Because the minute hand has traveled halfway around the clock, we can also say the time is half past 8. Say that with me.

STUDENTS DO: Say half past 8 with the teacher.

TEACHER SAY: Let’s try another one. I am going to pick a card and read it to you. Show that time on your clock and then check your work with your Shoulder Partner. Give me a Thumbs Up when you are ready.

TEACHER DO: Using the card set, pick a card and read it to the group. Write on the board what the card shows for a visual reference.

Note to the Teacher: This lesson uses 3:30/half past 3 as an example. Adjust the wording of this portion of the lesson to match the time you selected.

STUDENTS DO: Show the given time on their clock. Check work with Shoulder Partner. When done, give a Thumbs Up. Selected students write the time on the board.

TEACHER SAY: Nice job. The time was 3:30. That means that the hour hand is past 3 but not yet at 4. It is right in between, or halfway, between 3 and 4. The hour hand moved halfway between the hours, and the minute hand has gone halfway around the clock to the bottom, or the 6. Half of an hour has passed. Half an hour is 30 minutes, so we say 3:30.

TEACHER DO: Point to the 3:30 that the student wrote on the board. Point to the 3 and label the 3 “Hour” and the 30 “Minutes.”

TEACHER SAY: For the rest of the time today you and your Shoulder Partner will practice showing to the half hour on your clocks. You will get a set of cards. Pick a card. Both of you show the time and check each other’s work. Do you have any questions?

STUDENTS DO: Ask any clarifying questions about the activity.

TEACHER DO: Hand out Half-Hour Cards to each pair of students.

STUDENTS DO: Pick a card. Show the time on their clock. Compare answers with their Shoulder Partner. Repeat until the teacher uses an Attention Getting Signal.

TEACHER DO: Walk around the room and observe students as they work and talk to their Shoulder Partner. Note students who may need additional instruction or practice. Be sure students are moving the hour hand as well as the minute hand. When the Learn time is over, use an Attention Getting Signal to bring the group back.

TEACHER SAY: I saw so much great math work around the room. Stack up your cards, please. I will collect them while you put away your clocks. Take out your student book, and give your Shoulder Partner a high five.

STUDENTS DO: Take out student books, put away clocks, and give Shoulder Partner a high fi ve.

TEACHER DO: Collect card sets from students.