## What is Average Speed?

#### Important Formulas:

**Average speed**=

Total distance travelled |

Total time taken |

**Total distance travelled**= Average speed × Total time taken

**Total time taken**=

Total distance travelled |

Average speed |

#### 1. Understanding Average Speed

A car is going from City A to City B.

It starts from City A at 9:00 am and travels the first 30 km at 30 km/h.

Next, it is held in a traffic jam for

h.

Finally, it travels the next 15 km at 20 km/h and arrives in City B at 11:00 am.

No.

Total distance travelled by the car is 45 km.

Let's calculate the total time taken by the car to travel 45 km:

Time taken for the first 30 km --> 1 h

Time lost in the traffic jam -->

h

Time taken for the next 15 km -->

h

Total time taken = 1 h +

h +

h = 2 h

The car travelled a total distance of 45 km in a total of 2 h.

It travelled an average of 22.5 km in 1 h.

Its

It starts from City A at 9:00 am and travels the first 30 km at 30 km/h.

Next, it is held in a traffic jam for

1 |

4 |

Finally, it travels the next 15 km at 20 km/h and arrives in City B at 11:00 am.

**a) Does the car travel at the same speed throughout the journey?**No.

**b) What is the average speed of the car for the journey?**Total distance travelled by the car is 45 km.

Let's calculate the total time taken by the car to travel 45 km:

Time taken for the first 30 km --> 1 h

Time lost in the traffic jam -->

1 |

4 |

Time taken for the next 15 km -->

3 |

4 |

Total time taken = 1 h +

1 |

4 |

3 |

4 |

The car travelled a total distance of 45 km in a total of 2 h.

It travelled an average of 22.5 km in 1 h.

Its

**average speed**for the journey is 22.5 km/h.#### 2. An aeroplane takes

5 | 1 |

2 |

What is the average speed of the aeroplane?

Distance travelled = 4142 km

Time taken =

h =

h

= 4142 km ÷

h

= 4142 km ×

h

= 753.1 km/h

The average speed of the aeroplane is

Time taken =

5 | 1 |

2 |

11 |

2 |

**Average speed**= 4142 km ÷

11 |

2 |

= 4142 km ×

2 |

11 |

= 753.1 km/h

The average speed of the aeroplane is

**753.1 km/h**.#### 3. Julie cycles at a speed of 215 m/min.

How long does it take her to cycle a distance of 1500 m?

Round off your answer to the nearest minute.

Speed = 215 m/min

Distance travelled = 1500 m

= 1500 m ÷ 215 m/min

= 6.97 min

≈ 7 min

It takes her about 7

Distance travelled = 1500 m

**Time taken**= 1500 m ÷ 215 m/min

= 6.97 min

≈ 7 min

It takes her about 7

**minutes**.#### 3. A roller skater skates at an average speed of 35 km/h.

Find the distance he covers in 15 minutes.

Speed = 35 km/h

Time taken = 15 min =

h

h = 8.75 km

He covers a distance of

Time taken = 15 min =

1 |

4 |

**Distance covered**= 35 m/h ×1 |

4 |

He covers a distance of

**8.75 km**in 15 minutes.