Subtract time measurement

### 1.1. Knowledge to remember

**a) Example 1:**

A car leaves Hue at 13:10 and arrives in Da Nang at 15:55. How long does it take the car to go from Hue to Da Nang?

We have to do the subtraction: 15 hours 55 minutes – 13 hours 10 minutes = ?

We calculate and calculate as follows:

So: 15 hours 55 minutes – 13 hours 10 minutes = 2 hours 45 minutes.

**b) Example 2:**

On the same road, Hoa ran for 3 minutes and 20 seconds. The battery runs for 2 minutes 45 seconds. How many seconds does Binh run less than Hoa?

We have to do the subtraction:

3 minutes 20 seconds – 2 minutes 45 seconds = ?

We calculate and calculate as follows:

So: 3 minutes 20 seconds – 2 minutes 45 seconds = 35 seconds.

### 1.2. Solve textbook exercises on page 133

**Lesson 1 Textbook page 133**

Calculate:

a) 23 minutes 25 seconds – 15 minutes 12 seconds;

b) 54 minutes 21 seconds – 21 minutes 34 seconds;

c) 22:15 – 12:35.

**Solution guide:**

Lesson 2 Textbook page 133

Calculate:

a) 23 days 12 hours – 3 days 8 hours;

b) 14 days 15 hours – 3 days 17 hours;

c) 13 years 2 months – 8 years and 6 months.

*Solution guide:*

Lesson 3 Textbook page 133

A person leaves from A at 6:45 and arrives at B at 8:30. In the middle of the road he rested for 15 minutes. If not including rest time, how long does it take the person to travel AB?

*Solution guide:*

The time taken by the person to travel distance AB (excluding rest time) is:

8:30 a.m. – 6:45 a.m. – 15 minutes = 1 hour and 30 minutes

Answer: 1 hour 30 minutes.

### 1.3. Solving exercises in the textbook Practice page 134

**Lesson 1 Textbook page 134**

Write the correct number in the dot:

a) 12 days = … hours b) 1.6 hours = … minutes

3.4 days = … hours 2 hours 15 minutes =… minutes

4 days 12 hours = … hours 2.5 minutes = … seconds

\(\frac{1}{2}\) hours = … minutes 4 minutes 25 seconds = … seconds

__Solution guide:__

a) 12 days = 288 hours (24 hours x 12 = 288 hours)

3.4 days = 81.6 hours (24 hours x 3.4 = 81.6 hours)

4 days 12 hours = 108 hours (24 hours x 4 + 12 hours = 108 hours)

\(\frac{1}{2}\) hours = 30 minutes (60 minutes x \(\frac{1}{2}\) = 30 minutes )

b) 1.6 hours = 96 minutes (60 minutes x 1.6 = 96 minutes)

2 hours 15 minutes = 135 minutes (60 minutes x 2 + 15 minutes = 135 minutes)

2.5 minutes = 150 seconds (60 seconds x 2.5 = 150 seconds)

4 minutes 25 seconds = 265 seconds (60 seconds x 4 + 25 seconds = 265 seconds).

Lesson 2 Textbook page 134

Calculate:

a) 2 years 5 months + 13 years and 6 months;

b) 4 days 21 hours + 5 days 15 hours;

c) 13 hours 34 minutes + 6 hours 35 minutes.

__Solution guide:__

Lesson 3 Textbook page 134

Calculate:

a) 4 years 3 months – 2 years 8 months;

b) 15 days 6 hours – 10 days 12 hours;

c) 13 hours 23 minutes – 5 hours 45 minutes.

__Solution guide:__

Lesson 4 Textbook page 134

In 1492, the explorer Christopher Columbus discovered America. In 1961, Iuri Gagarin was the first person to go into space. How many years apart are these two events?

__Solution guide:__

The two events separated by a number of years are:

1961 – 1492 = 469 (years)

Answer: 469 years.

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