Time

### 1.1. Knowledge to remember

**a) Problem 1:**

A car travels 170 km at a speed of 42.5 km/hr. Calculate the time taken by the car to travel that distance.

Solution:

Car travel time is:

170 : 42.5 = 4 (hours)

Answer:

$4$hours.

*Comment *: To calculate the travel time of the car we take the distance traveled divided by the distance the car traveled in 1

hour or speed of the car.

To calculate time, divide the distance by the speed.

We have: t = s : v

**b) Problem 2:**

A canoe travels at a speed of 36km/hr over a 42km river. Calculate the travel time of the canoe on that distance.

Solution:

The travel time of the canoe is:

42 : 36 = \(\frac{7}{6}\)(hour)

\(\frac{7}{6}\)

$\frac{\mathrm{}}{}$hour =1\(\frac{1}{6}\) hours

$=\mathrm{first}$hours

$ten$minute.

Answer: 1

$first$hour 10 minutes.

### 1.2. Solve textbook exercises on page 143

**Lesson 1 Textbook page 143**

Write the correct number in the blank:

s (km) | 35 | 10.35 | 108.5 | 81 |

v (km/h) | 14 | 4.6 | 62 | 36 |

t (hour) |

__Solution guide:__

s (km) | 35 | 10.35 | 108.5 | 81 |

v (km/h) | 14 | 4.6 | 62 | 36 |

t (hour) | 2.5 | 2.25 | 1.75 | 2.25 |

Lesson 2 Textbook page 143

a) On a distance of 23.1 km, a cyclist travels at a speed of 13.2 km/hr. Calculate the person’s travel time.

b) On a distance of 2.5 km, a person runs at a speed of 10 km/hr. Calculate the person’s running time.

__Solution guide:__

a) The cyclist’s travel time is:

23.1 : 13.2 = 1.75 = 1 hour 45 minutes

b) The person’s running time is:

2.5 : 10 = 0.25 (hour) = 15 minutes

Answer: a) 11:45 am;

b) 15 minutes.

Lesson 3 Textbook page 143

An airplane traveling at 860 km/hr covers a distance of 2150 km. What time does the plane arrive, if it leaves at 8:45?

__Solution guide:__

The time taken by the plane to travel that distance is:

2150 : 860 = 2.5 (hours)

Change 2.5 hours = 2 hours 30 minutes.

Plane arrives at:

8 hours 45 minutes + 2 hours 30 minutes = 10 hours 75 minutes

10 hours 75 minutes = 11 hours 15 minutes (because 75 minutes = 1 hour 15 minutes)

Answer: 11:15 a.m.

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