Speed, distance, time
S = D ÷ T. Speed-distance-time triangle. Compound measure introduced in Year 8.
Speed = distance ÷ time. Rearrange via the SDT triangle: D = ST, T = D/S. Units must be consistent: km/h with km and hours; m/s with metres and seconds.
Worked examples
120 miles in 2 hours = 60 mph.
30 m/s × 5 s = 150 m.
30 m/s = 108 km/h. Multiply by 3.6.
Frequently asked questions
Why mph in the UK?
Road speeds in the UK use miles per hour by statute. Maths exams may use mph or km/h; check units.
Average vs constant speed?
KS3 assumes constant. Average speed = total distance ÷ total time, which differs from the average of two speeds.