Appears in: Functional Skills Level 2 · GCSE foundation
Speed, distance and time
Speed, distance and time is the compound measure that turns up most on Functional Skills Level 2 and GCSE foundation papers. The formula is simple; the marks are usually lost on converting the time. Two hours fifteen minutes is not 2.15 hours.
The method
- Speed = distance ÷ time. Distance = speed × time. Time = distance ÷ speed. Cover the one you want in the triangle (D on top, S and T underneath) and what's left tells you the calculation.
- Convert the time into a decimal number of hours before you calculate: minutes ÷ 60. 15 minutes is 0.25 h, 30 is 0.5, 45 is 0.75, 20 is 0.333….
- Convert a decimal answer back into minutes at the end: the decimal part × 60. 2.25 hours is 2 hours and 0.25 × 60 = 15 minutes.
- Density works exactly the same way: density = mass ÷ volume.
Worked examples
Example 1
A van travels 135 miles in 2 hours 15 minutes. What is its average speed?
- 2 hours 15 minutes = 2 + 15 ÷ 60 = 2.25 hours.
- Speed = 135 ÷ 2.25 = 60 mph.
Example 2
How long does it take to drive 90 miles at an average of 40 mph?
- Time = distance ÷ speed = 90 ÷ 40.
- = 2.25 hours, which is 2 hours 15 minutes (0.25 × 60 = 15).
Example 3
A cyclist rides at 50 km/h for 1 hour 36 minutes. How far do they go?
- 1 hour 36 minutes = 1 + 36 ÷ 60 = 1.6 hours.
- Distance = 50 × 1.6 = 80 km.
Example 4
A block has a mass of 540 g and a volume of 200 cm³. What is its density?
- Density = mass ÷ volume = 540 ÷ 200 = 2.7 g/cm³.
Where the marks go missing
- Typing 2 hours 15 minutes as 2.15. Minutes are out of 60, not 100: it's 2.25.
- Leaving a time answer as a decimal when the question wants hours and minutes — or reading 2.5 hours as 2 hours 50.
- Mixing units: a speed in mph with a time in minutes. Get everything into hours (or everything into minutes) first.
Frequently asked questions
What is the formula for speed?
Speed = distance ÷ time. Rearranged: distance = speed × time, and time = distance ÷ speed.
How do I convert minutes to hours for speed questions?
Divide the minutes by 60 and add to the whole hours. 1 hour 40 minutes is 1 + 40 ÷ 60 = 1.667 hours.