When we know the distance traveled and the time taken, we can find the speed using:

$Speed = \frac{Distance}{Time}$

Worked Example 1

A bus travels 120 kilometres in 3 hours. What is its speed?

Solution

• Distance = 120 km
• Time = 3 hours

$Speed = \frac{120 \text{ km}}{3 \text{ h}} = 40 \text{ km/h}$

The bus travels at 40 kilometres per hour.

Worked Example 2

Mwinyimkuu ran 80 metres in 20 seconds. Find his speed in metres per second.

Solution

$Speed = \frac{80 \text{ m}}{20 \text{ s}} = 4 \text{ m/s}$

When we know the speed and the time, we can find the distance traveled:

$Distance = Speed \times Time$

Worked Example 3

A motorcycle travels at a speed of 50 kilometres per hour for 4 hours. How far does it travel?

Solution

• Speed = 50 km/h
• Time = 4 hours

$Distance = 50 \text{ km/h} \times 4 \text{ h} = 200 \text{ km}$

The motorcycle travels 200 kilometres.

Worked Example 4

Amina walks to school at a speed of 5 kilometres per hour. If she walks for 30 minutes (0.5 hours), what distance does she cover?

Solution

$Distance = 5 \text{ km/h} \times 0.5 \text{ h} = 2.5 \text{ km}$

Amina covers 2.5 kilometres.

When we know the distance and the speed, we can find how long the journey takes:

$Time = \frac{Distance}{Speed}$

Worked Example 5

The distance from Dodoma to Iringa is 256 kilometres. A car travels at a speed of 64 km/h. How long does the journey take?

Solution

$Time = \frac{256 \text{ km}}{64 \text{ km/h}} = 4 \text{ hours}$

The journey takes 4 hours.

Worked Example 6

A cyclist covers 300 metres at a speed of 6 metres per second. How much time does the cyclist use?

Solution

$Time = \frac{300 \text{ m}}{6 \text{ m/s}} = 50 \text{ seconds}$

• Always check that your units are the same before solving. For example, if distance is in kilometres and time is in hours, speed will be in km/h.
• When time is given in minutes, convert it to hours by dividing by 60.
• Read the problem carefully and identify what you need to find: distance, time, or speed.
• Use the correct formula based on what you need to find.

In Tanzania, farmers often need to calculate how long it will take to transport their produce from the farm to the market. For example, if a farmer transports maize to the market in Morogoro town, traveling 60 km at a speed of 30 km/h, the farmer can use the time formula to know that the journey will take 2 hours and plan when to leave. This helps them arrive at the market on time to sell their goods.