Speed, Distance and Time

In short: Speed, distance and time are linked: distance = speed × time, speed = distance ÷ time, and time = distance ÷ speed. Make sure the units match, so a speed in km/h needs the time in hours.

Before you start

• Fractions of an hour: $\frac{1}{2}$ h $=30$ min, $\frac{1}{4}$ h $=15$ min, 1 min $=\frac{1}{60}$ h (see Metric Units and Conversions).
• Multiplying and dividing decimals.
• km/h means kilometres per hour: how many kilometres in one hour.

The speed triangle

Minutes and km/h

km/h to metres per second

1 km/h $=1000$ m in $3600$ seconds. So to change km/h into m/s, divide by 3.6.

$36$ km/h $=36÷3.6=10$ m/s.

Trains and tunnels

Meeting problems

When two people move towards each other, the gap closes at the sum of their speeds.

Quick summary

• Distance $=$ speed $\times$ time. Speed $=$ distance $÷$ time. Time $=$ distance $÷$ speed.
• Match the units: km/h needs time in hours.
• 30 min $=\frac{1}{2}$ h, 20 min $=\frac{1}{3}$ h, 15 min $=\frac{1}{4}$ h, 6 min $=\frac{1}{10}$ h.
• 60 km/h is 1 km per minute.
• A train passing through a station travels the station length plus its own length.
• Moving towards each other, add the speeds.

Quiz