Why Do we Count by 5s?
Lesson 4 of 9
Objective: SWBAT make connections between counting by 5s and the minute hand.
Setting Up the Learning
A key aspect of the CCSS shift is the push towards students developing a conceptual understanding of mathematics. In this lesson, students understand why we count by 5s, instead of just memorizing the idea of half hour. This also allows students to connect to their understanding of why we group-count in general, which gets at number sense concepts.
Yesterday we talked about how the minute hand says "00" when it points to the 12. We use the word "o'clock" to describe this time. Today we will talk about WHY the minute hand says 00 there.
We use the clock to tell the time and measure the time everyday. In football, they have to measure how long each quarter of the game is in minutes. In school, we have to check the clock to see what time it is.
Your thinking job today is: How does the minute hand count?
Counting Around the Clock:
- The minute hand looks at the little lines between the big numbers.
- We are only going to say the numbers loud when we get to the big numbers. (Whisper count 1-4 and say 5 loud)
- Let’s do that together and say the numbers loud and I’ll write them down. (I'll puts a post it over the big numbers with the minute hand info)
- Let me say the numbers that we wrote down. How are we counting?
- Discuss the WHY: We count by 5s because each part of the clock has 5 minutes in it (model checking each section to make sure there are 5 minutes between the big numbers).
Practice figuring out what the minute hand is saying on teacher clock.
Add to time anchor chart:
“When we tell time, we have to follow these steps to figure out and write the time”
- Start with the hour hand. Circle it.
- Is the hour hand pointing to a number or in the middle?
- Look at the minute hand.
- Count by 5s.
Partner Talk: Why do we have to count by 5s?
Students add to paper plate clocks: We started making these clocks in this lesson!
Students write the numbers they say around the outside rim of the paper plate.
- On your clocks today, you are going to add in what the minute hand sees and says on the outside of the plate.
- How will you figure out what the minute hand says on each part of the clock?
- Do 00 together at the 12, then do 1, 2, and 3 together. (05, 10, 15)
- Compare with your partner’s. Does your plate have the same numbers going around it?
- Put your minute hand on the 25 mark. What number is it pointing to?
- Follow this routine with other minute hand times. If students need a challenge, add in hour information. (The time is 2:40. Where will the hour hand go? Where will the minute hand go?)
Students show how to count by 5s by labeling the clock. Students draw the minute hand to point at the number that represents the minute.
Students order clocks from 1:00 to 2:00. Students cut out the clock to represent the time.
Group C Extension: See Extension video for more on the Group C work.
Students use the exercise schedule clues to figure out what time each exercise starts. Students use critical thinking skills to interpret clues and order the exercises.
Pass out post its/cards that say 00 all the way to 60 by 5s. Have students figure out where to put them to label the classroom clock.