Students Professional
JA EN
Student mode › Grade 6
FREE ·Grade 6

Speed

Where this is used

Speed is how far you travel in one hour. It is the classic example of a rate: an amount per one unit. The same idea shows up everywhere once you look for it, in pay per hour, fuel per liter, internet speed, and how many items a factory can make in an hour.

Key points

Speed = distance ÷ time

A car that travels 180 km in 3 hours is going 180 ÷ 3 = 60 km/h. That number tells you how far it goes in one hour. Because everything is scaled down to one hour, you can compare any two cars fairly.

A car at 60 km/h makes a straight line
0100200300400km00 h601 h1202 h1803 h2404 h

Three formulas are really just one

Distance = speed × time, and time = distance ÷ speed. You do not have to memorize all three. Learn "speed = distance ÷ time" and rearrange it when you need to. Like a balance scale, an equation stays true as long as you do the same thing to both sides.

speed × time distance Know any two of them and you can work out the third

Match the units before you calculate

You cannot put 60 km/h and 30 minutes straight into the formula. Change 30 minutes into 0.5 hours first, then 60 × 0.5 = 30 km. Forgetting to match the time units is the most common mistake here, and it throws the answer off by a factor of 60.

On a graph, the steepness is the speed

Put time along the bottom and distance up the side, and the faster car draws the steeper line. The steepness of the line is the speed. The slope of a linear function in middle school, and calculus in high school, are this same idea taken further.

The faster the car, the steeper the line
hourskm60 km/h30 km/h

Check yourself 5questions

Tap an option to check

Q1 A car travels 180 km in 3 hours. What is its speed?

Q2 How far do you travel in 30 minutes at 60 km/h?

Q3 How long does it take to drive 120 km at 40 km/h?

Q4 On a graph of time against distance, what does a steeper line mean?

Q5 What is the most common mistake in speed problems?

Jobs that use this

Every job uses this. The ones below are just where it shows up most.

Pilot / ship's navigator $150k
Delivery route planner $68k
Network engineer $110k

Pilot / ship's navigator$150k

They work out arrival times from speed, distance and time, then adjust for wind and ocean currents. Fuel burns by the hour, so a mistake in the math can cost lives.

Maths used: SpeedRates (amount per unit)Vectors

Delivery route planner$68k

They use speed to predict when each truck will arrive and decide what order to make the deliveries in. The number of stops a truck can finish in a day is the company's revenue.

Maths used: SpeedWorking with timeOptimization

Network engineer$110k

They estimate how long a file transfer will take from the connection speed, measured in megabits per second. The math is the same whether what is moving is a car or data.

Maths used: SpeedRates (amount per unit)Computational complexity

Comments

Sign in to comment

All grades