Reviewing calculations with time measurements

### 1.1. Solve textbook exercises on page 165,166

**Lesson 1 Textbook page 165**

Calculate

a) 12 hours 24 minutes + 3 hours 18 minutes b) 5.4 hours + 11.2 hours

14 hours 26 minutes – 5 hours 42 minutes 20.4 hours – 12.8 hours

__Solution guide:__

a)

b)

Lesson 2 Textbook page 165

Calculate

a) 8 minutes 54 seconds x 2 b) 4.2 hours x 2

38 minutes 18 seconds : 6 37.2 minutes : 3

__Solution guide:__

a)

b)

Lesson 3 Textbook page 16

A cyclist covers a distance of 18 km at a speed of 10 km/hr. How long did it take the cyclist?

__Solution guide:__

The time it takes the cyclist to cover the distance is:

18 : 10 = 1.8 (hours)

1.8 hours = 1 hour 48 minutes

Answer: 1 hour 48 minutes.

Lesson 4 Textbook page 166

A car leaves Hanoi at 6:15 and arrives in Hai Phong at 8:56. In the middle of the road, the car stops for 25 minutes. The speed of the car is 45km/h. Calculate the distance from Hanoi to Hai Phong.

__Solution guide:__

Excluding the rest time, the time it takes to travel from Hanoi to Hai Phong is:

8 hours 56 minutes – 6 hours 15 minutes – 25 minutes = 2 hours 16 minutes

Change: 2 hours 16 minutes = \(2\frac{{16}}{{60}}\) hours = \(2\frac{{4}}{{15}}\) hours = \(\frac{{34}}{{15}}\) hours.

Distance from Hanoi to Hai Phong is:

45 x \(\frac{{34}}{{15}}\) = 102 (km)

Answer: 102km.

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