Start Free
Level 6Grade 6skill: speed_distance_time· 9 min read

Speed, Distance and Time Made Simple

In short: Every speed-distance-time question comes from one equation: speed = distance ÷ time. Know two of the three and you rearrange for the third — divide to find speed or time, multiply to find distance. The real skill is units: make the distances and times consistent before you calculate.

One relationship, three questions

Speed = distance ÷ time. That single line is the whole topic. Every speed-distance-time question is really just asking you to rearrange it — or to fix the units before you rearrange it.

There are exactly three things you can be asked to find, and they come from the same equation. If you know the distance and the time, you divide to get speed. If you know the speed and the time, you multiply to get distance. If you know the distance and the speed, you divide to get time.

There's one more thing worth knowing: the units decide the operation for you. Kilometres divided by hours gives km/h, which is a speed. Kilometres per hour multiplied by hours gives kilometres, which is a distance. If the units of your answer don't match what the question asked for, you picked the wrong operation — no memorising required.

  1. Write down the two quantities you know and the one you want.
  2. Choose the form: speed = distance ÷ time, distance = speed × time, or time = distance ÷ speed.
  3. Check the units agree — all in hours or all in minutes, all in km or all in metres. If they don't, convert first.
  4. Do the arithmetic carefully, keeping any decimal.
  5. Check that the units of your answer match what the question asked for.

Why one equation covers everything Why it works

Find speed
distance ÷ time

240 km ÷ 4 h = 60 km/h

Find distance
speed × time

15 km/h × 3 h = 45 km

Find time
distance ÷ speed

180 km ÷ 60 km/h = 3 h

Units must agree
convert so the two known values share a unit before you calculate

15 min = 15 ÷ 60 = 1/4 h, so at 80 km/h you travel 80 × 1/4 = 20 km

The units are a free error-check built into the question. Track them through your working and a wrong operation reveals itself before you ever reach the answer — km ÷ h can only be a speed, never a distance, and km/h × h can only be a distance, never a speed. Let the units of your answer confirm you picked the right operation.

Worked examples

A car travels 240 km in 4 hours. What is its speed? = 60 km/h
  1. You know distance and time and want speed, so use speed = distance ÷ time.
  2. 240 ÷ 4 = 60.
A cyclist rides at 15 km/h for 3 hours. How far does she go? = 45 km
  1. You know speed and time and want distance, so use distance = speed × time.
  2. 15 × 3 = 45.
A train covers 180 km at a steady 60 km/h. How long does the journey take? = 3 hours
  1. You know distance and speed and want time, so use time = distance ÷ speed.
  2. 180 ÷ 60 = 3.
A car drives at 90 km/h. How far does it travel in 20 minutes? = 30 km
  1. Distance = speed × time, but the speed is per hour and the time is in minutes — the units clash.
  2. Convert first: 20 minutes = 20 ÷ 60 = 1/3 of an hour.
  3. 90 × 1/3 = 30.
  4. Because the units now agree, the answer is a clean distance in kilometres.
A cyclist covers 12 km at a steady 16 km/h. How long does the ride take, in minutes? = 45 minutes
  1. You know distance and speed and want time, so use time = distance ÷ speed.
  2. 12 ÷ 16 = 0.75, so the ride takes 0.75 of an hour.
  3. The question asks for minutes, so convert back: 0.75 × 60 = 45.
  4. The answer's unit is minutes — exactly what was asked.

Mistakes that cost marks

Multiplying when you should divide

✗ 960 km/h

For "240 km in 4 hours, find the speed" this multiplies 240 × 4 = 960 instead of dividing. It reaches for speed × time out of habit, but you don't yet know the speed — that's the thing you're solving for.

Fix: Ask what you're finding. Finding speed always means distance ÷ time. The giveaway: 960 km/h would mean covering 960 km every hour, so the 240 km trip would take 15 minutes, not 4 hours — clearly wrong.

wrong_operation

Putting the decimal point one place off

✗ 75 km/h

For "45 km in 6 hours", 45 ÷ 6 = 7.5. Writing 75 slides the decimal point one position and inflates the answer tenfold.

Fix: Sanity-check the size. At 75 km/h you'd finish 45 km in well under an hour, yet the trip took 6 hours — so the speed must be small. 7.5 km/h fits; 75 doesn't.

decimal_point_shift

Stopping at the remainder instead of finishing the decimal

✗ 37 km/h

For "150 km in 4 hours", 150 ÷ 4 = 37 remainder 2. Reporting 37 stops one step early — the leftover 2 still needs to become part of the answer.

Fix: Convert the remainder: 2 ÷ 4 = 0.5, so the full answer is 37.5 km/h. A remainder in a speed-distance-time answer almost always means a decimal, not a stopping point.

partial_computation

Mixing minutes with hours

✗ 1800 km

For "90 km/h for 20 minutes", this does 90 × 20 = 1800, treating 20 minutes as 20 hours. The speed is per hour but the time was left in minutes, so the units never matched.

Fix: Convert before multiplying: 20 minutes = 20 ÷ 60 = 1/3 hour. Then 90 × 1/3 = 30 km — a sensible distance for a third of an hour.

unit_mismatch

Practice speed, distance and time

Work through a set that mixes all three forms of the relationship — plus a few that hide a unit conversion. Watch your units at every step and finish the decimals.

Skills that connect here

First, make sure of

Frequently asked questions

What is the formula for speed?

Speed = distance ÷ time. From that one equation you can also get distance = speed × time and time = distance ÷ speed, just by rearranging.

How do I decide whether to multiply or divide?

Let the units guide you. Finding a speed means dividing a distance by a time (km ÷ h = km/h). Finding a distance means multiplying speed by time (km/h × h = km). If the units of your answer don't match what the question asked for, you chose the wrong operation.

How do I turn minutes into hours?

Divide the minutes by 60. So 20 minutes = 20 ÷ 60 = 1/3 hour, and 90 minutes = 90 ÷ 60 = 1.5 hours. Always convert so both known quantities share the same unit before you calculate.

What should I do when the division leaves a remainder?

Turn it into a decimal rather than stopping. For 150 ÷ 4 you get 37 remainder 2, and 2 ÷ 4 = 0.5, so the answer is 37.5. In speed-distance-time problems a remainder almost always becomes a decimal part of the answer.

What units is speed usually measured in?

Kilometres per hour (km/h) for cars and trains, and metres per second (m/s) for shorter, faster events like sprinting. Whichever you use, keep the distance and time units consistent with it.