How to tell time, write time and convert time – Maths 3

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Hôm nay chủ đề chúng ta tìm hiểu là “Time” – Thời gian.

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Toán tiếng Anh tiểu học (G1-G5)

Telling and writing time

Look at the clock face. There are 60 small markings on it.

Nhìn vào mặt đồng hồ. Ta có thể thấy có 60 vạch nhỏ trên đó.

Remember:

• Each small mark between the numbers on the clock stands for 1 minute.
• It takes 5 minutes for the minute hand to move from one number to the next.

Nhớ rằng:

• Mỗi vạch nhỏ giữa các số trên đồng hồ là một phút.
• Mất 5 phút để kim phút dịch chuyển từ một số sang số tiếp theo.

There are some ways to say time.

Duration of time

We use a clock face to find the duration of time in Primary 2.

In Primary 3, we can use the timeline to help us find the duration of time.

Now, let’s learn to draw the timeline.

Ở lớp 2 chúng ta sử dụng đồng hồ để tìm khoảng thời gian. Ở lớp 3, chúng ta có thể dùng trục thời gian như sau để tìm khoảng thời gian.

Ex: Find the duration of time between 10 a.m. to 3 p.m.

• First draw a horizontal line with regular intervals.
• Then number the intervals from 10 a.m. to 3 p.m. This means that each interval is 1 hour.
• Lastly, count the number of intervals between 10 a.m. to 3 p.m. That will give us the duration.

The duration is 5 hours.

Remember:

• A.M. is used for the hours from 12 midnight to 12 noon.
• P.M. is used for the hours from 12 noon to 12 midnight.

Note that the timeline can be drawn to show intervals in minutes and hours.

Converting time

Units of Time

The units of time are hour (h), minute (min), year, month, week, and day.

Các đơn vị tính thời gian là giờ, phút, năm, tháng, tuần và ngày.

1 hour is 60 times as long as 1 minute	1h = 60 min
1 year is 12 times as long as 1 month	1 year = 12 months
1 month can be 28, 29, 30, or 31 times as long as 1 day	1 month = 28 days 1 month = 29 days 1 month = 30 days 1 month = 31 days
1 week is 7 times as long as 1 day	1 week = 7 days
1 day is 24 times as long as 1 hour	1 day = 24 hours

Note that the number of days in a month is different for different months of the year.

Take out a calendar and have a closer look at the months.

You will notice the following:

1. February has 28 days althought in a leap year, which comes once every 4 years, it will have 29 days.
2. January, March, May, July, August, October and December have 31 days.
3. April, June, September and November have 30 days.
4. There are 52 weeks in a year.
5. There are 365 days in a year or 366 days in a leap year.

Ex: Convert 2 h 46 min to minutes

Solution: 1 h = 60 min

2 h = 120 min

Then, 2 h 46 min = 120 min + 46 min = 166 min

Adding time

We can add time using a few methods. They are:

Method 1:

Step 1: Add the bigger unit first. Regroup if necessary.

Step 2: Then add the smaller unit.

For example,

Add 6 h 27 min to 2 h 45 min.

Solution:

6 h 27 min + 2h = 8 h 27 min

8 h 27 min + 45 min = 8 h 72 min (We regroup 60 min as 1 h so, 72 min = 1h 12 min)

= 9 h 12 min

So, 6 h 27 min + 2 h 45 min = 9 h 12 min

Method 2:

Arrange the numbers in columns before adding the smaller unit followed by the bigger unit.

Step 1: Add the minutes. Regroup if necessary.

Step 2: Add the hours.

Subtracting time

Subtracting time is similar to adding time.

For example,

7 h 20 min – 5 h 15 min

Solution:

7 h 20 min – 5 h = 2 h 20 min

2 h 20 min – 15 min = 2h 5 min

Then, 7 h 20 min – 5 h 15 min = 2 h 5 min

Solving word problems involving time

Example 1.

Tom watched a movie from 1:15 p.m. to 3:25 p.m. How long did the movie last?

Solution:

45 min + 1 h = 1 h 45 min

1 h 45 min + 25 min = 2 h 10 min.

The movie lasted 2 h 10 min.

Example 2.

Connor volunteers with his mom at an animal shelter every Wednesday. He arrives at 4:00 p.m. and leaves at 5:30. How long is he at the animal shelter?

Solution:

Answer: 1 h 30 min

Let’s practice

Problem 1.

Michael’s watch shows 6:10 p.m. His watch is 10 minutes fast. What is the actual time?

Problem 2.

Lisa 3 h 5 min to paint a picture. She started painting at 11: 30 a.m. At what time did she paint the picture?

Problem 3.

Kelvin started reading at 2:15 p.m. He took a break at 3: 45 p.m. How long did Kelvin read before he took a break?

Xem thêm các bài viết Toán tiếng Anh tiểu học chủ đề khác:

Toán tiếng Anh tiểu học (G1-G5)

Như vậy, chúng ta đã cùng tìm hiểu kiến thức và từ vựng Toán tiếng Anh chủ đề “Time” – Math Grade 3.

Chúc các bạn học tốt!

More about Time – AM/PM vs 24 Hour Clock

Th.s Toán

Nguyễn Thùy Dung