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Detailed notes on Algebra for Cambridge IGCSE Mathematics, covering key concepts, explanations, examples, and exam-focused revision points.
Two graphs, two interpretations. Distance-time gradient = speed; speed-time area = distance. Master both and motion problems on Paper 4 become a 5-mark gift.
Mapped to the Cambridge IGCSE 0580 syllabus (2025-2027).
Time on the x-axis, distance on the y-axis. Gradient gives speed.
Reading a distance-time graph.
| Feature | Meaning |
|---|---|
| Straight line, positive gradient | Constant speed (away from start) |
| Straight line, negative gradient | Constant speed (returning toward start) |
| Horizontal line | Stationary |
| Steeper slope | Faster |
The gradient between any two points is the AVERAGE SPEED over that interval: speed=ΔtΔd=change in timechange in distance.
Worked. A car travels 400 m from t=0 to t=80 s, then stays parked from 80 to 100 s, then returns 400 m from 100 to 200 s.
Total distance vs displacement. A d-t graph showing the runner returning to start has TOTAL distance =800 m but final DISPLACEMENT =0.
Time on the x-axis, speed on the y-axis. Gradient = acceleration; AREA UNDER = distance.
Reading a speed-time graph.
| Feature | Meaning |
|---|---|
| Horizontal line | Constant speed |
| Positive gradient (rising) | Accelerating |
| Negative gradient (falling) | Decelerating |
| Returning to zero | Coming to a stop |
Two formulas.
Worked. A vehicle accelerates from rest to 20 m/s over 5 seconds, holds 20 m/s for 10 seconds, then decelerates uniformly to rest in 4 seconds. Find the total distance.
The graph has three regions:
Total: 50+200+40=290 m.
Acceleration in each phase.
Total distance / total time. Watch units.
Average speed for a complete journey: vˉ=total timetotal distance.
This is NOT the arithmetic mean of segment speeds — see the Speed/Distance/Time notes for the trap.
Average acceleration between two times: aˉ=tfinal−tinitialvfinal−vinitial.
Unit conversions (covered in the Speed/Distance/Time notes):
Always check that the question's units match your computation.
Verbatim phrases and definitions Cambridge mark schemes credit.
Travel graphs appear most years on Paper 4 as a 5-7 mark question, often combining d-t and s-t interpretation. Paper 2 has simpler 2-3 mark items. Examiner reports flag confusing d-t with s-t (mixing area and gradient), and computing simple-mean instead of total-distance-over-total-time for average speed.
Sources: Cambridge IGCSE Mathematics 0580 syllabus 2025-2027 (E2.16); 0580/42 Oct/Nov 2024 — Q11 (multi-leg speed-time); 0580 Examiner Reports 2022-2024. Last reviewed 2026-05-05.
Step-by-step solutions to past-paper-style questions on travel graphs, written exactly the way a tutor would explain them at the board.
Almost every travel graphs exam question is one of these shapes. Learn to spot each one and you will always know how to start.
Recognise it by
The question gives — or asks you to draw — a distance-time or speed-time graph, quoting segments, plateaus or corner coordinates.
How to approach it
Check the y-axis label first. On a distance-time graph the gradient is speed; on a speed-time graph the gradient is acceleration and the area under it is distance — decompose the area into triangles, rectangles and trapezia.
Common trap
Mixing up the two graph types, or plotting a return journey on a distance-time graph as an upward segment. Examiner reports flag the return as downward — distance is measured from the start.
Recognise it by
A real-world journey described in words — stages, stops and rests — with no graph drawn, asking for total distance or average speed.
How to approach it
Compute each stage's distance with d=vt, total the distances and total the times, then average speed =total timetotal distance.
Common trap
Leaving the stationary rest period out of the total time. Examiner reports flag this — excluding stops inflates the average speed.
Recognise it by
Several quantities chained — an acceleration phase, a constant-speed phase and a stated total distance — with an unknown time or speed to find.
How to approach it
Break the journey into its phases, write each phase's distance as an area (triangle or rectangle), add them, set the sum equal to the given total and solve for the unknown.
Common trap
Treating an acceleration phase as constant speed and using d=v×t on a sloped region. Examiner reports flag the sign and unit slips this causes — use the area method.
Question
On a distance-time graph, a runner covers 400 metres in 80 seconds (constant speed). What is her speed in m/s and km/h?
Step-by-step solution
Step 1
Speed = gradient = ΔtΔd.
v=80400=5m/s
Step 2
Convert m/s → km/h by multiplying by 3.6.
5×3.6=18km/h
Answer
5m/s=18km/h
Question
A car travels 60km in 1h, stops for 30min, then travels 90km in 1.5h. Find the average speed for the whole journey.
Step-by-step solution
Step 1
Total distance.
60+90=150km
Step 2
Total time, including the stop.
1+0.5+1.5=3h
Step 3
Average speed.
vˉ=3150=50km/h
Answer
50km/h
Examiner tip
Include the stationary period in total time. Excluding it gives a higher (wrong) average speed.
Question
A car accelerates uniformly from 5m/s to 25m/s in 4seconds. Find the acceleration.
Step-by-step solution
Step 1
Acceleration = gradient of speed-time graph.
a=ΔtΔv=425−5=5m/s2
Answer
a=5m/s2
Question
A car accelerates from rest to 20m/s in 4s, then travels at 20m/s for 10s, then decelerates to rest in 6s. Find the total distance travelled.
Step-by-step solution
Step 1
Distance = area under the speed-time graph. The shape is a trapezium with parallel sides 10 and 4+10+6=20.
Step 2
Trapezium area.
Area=21(a+b)×h=21(10+20)(20)=300
Answer
300m
Examiner tip
The trapezium method works whenever the graph has a constant-speed plateau between acceleration and deceleration. Decompose into triangles + rectangle if the shape is awkward.
Question
A walker's distance-time graph has two straight segments: from (0,0) to (20min,1.2km), then (20min,1.2km) to (50min,3.6km). Find her speed during each stage in km/h.
Step-by-step solution
Step 1
Stage 1: gradient =20−01.2−0=0.06km/min.
Step 2
Convert: 0.06×60=3.6km/h.
Step 3
Stage 2: gradient =50−203.6−1.2=302.4=0.08km/min.
Step 4
Convert: 0.08×60=4.8km/h.
Answer
Stage 1: 3.6km/h; Stage 2: 4.8km/h.
Question
A cyclist travels for 2h at 15km/h, rests for 0.5h, then travels for 1h at 25km/h. Find the total distance and her average speed for the whole journey.
Step-by-step solution
Step 1
Distance covered in each moving stage.
d1=15×2=30km; d2=25×1=25km
Step 2
Total distance.
30+25=55km
Step 3
Total time = moving + rest.
2+0.5+1=3.5h
Step 4
Average speed.
vˉ=3.555≈15.7km/h
Answer
Total distance 55km; average speed ≈15.7km/h.
Question
A boy walks 400m to school in 5 minutes, stays at school for 10 minutes, then runs back home covering 400m in 4 minutes. Describe the distance-time graph: state coordinates of the corner points.
Step-by-step solution
Step 1
Starting point (0,0).
Step 2
After 5 min he is 400m from home: (5,400).
Step 3
Stationary for 10 min — horizontal segment to (15,400).
Step 4
Returns home in 4 min — line down to (19,0).
Answer
Plot (0,0)→(5,400)→(15,400)→(19,0), joining with straight line segments.
Examiner tip
The examiner report flags candidates who plot the return journey as ANOTHER positive segment (treating distance as a total). Distance-time means distance from START — the return is downward.
Question
A train decelerates uniformly from 30m/s to a stop over 24seconds. Find the deceleration.
Step-by-step solution
Step 1
Acceleration =ΔtΔv=240−30=−1.25m/s2.
Step 2
Magnitude of deceleration is 1.25m/s2.
Answer
Deceleration =1.25m/s2.
Examiner tip
State deceleration as a POSITIVE value (the magnitude). The examiner report flags students who leave the negative sign in the final 'deceleration' answer.
Question
A car accelerates uniformly from rest for 10s, reaching 20m/s. It then travels at 20m/s for T seconds. The total distance travelled in this (10+T)-second period is 500m. Find T.
Step-by-step solution
Step 1
Distance during acceleration = triangle area.
d1=21×10×20=100m
Step 2
Distance at constant speed = rectangle area.
d2=20T
Step 3
Set total equal to 500m.
100+20T=500
Step 4
Solve.
20T=400⇒T=20s
Answer
T=20seconds.
Examiner tip
The examiner report flags candidates who use d=v×t with the average speed for the acceleration phase but make sign / unit slips. Stick to the AREA-UNDER-GRAPH method: triangles, rectangles, trapezia.
The formulae you need to memorise for travel graphs on the Cambridge IGCSE 0580 paper, with every variable defined in plain English and a note on when to use it.
v=ΔtΔd
When to use
Gradient of a distance-time graph gives the speed at that interval.
a=ΔtΔv
When to use
Gradient of a speed-time graph gives the acceleration.
d=area under the graph
When to use
Area = total distance for that section. Decompose into triangles, rectangles or trapezia.
A=21(a+b)×h
When to use
Common shape under speed-time graphs with a plateau.
Definitions to memorise and the exact keywords mark schemes credit for travel graphs answers — sharpened from recent examiner reports for the 2026 0580 sitting.
Graph with time on the horizontal axis and distance from start on the vertical axis. Gradient = speed.
Graph with time on the horizontal axis and speed on the vertical axis. Gradient = acceleration; area = distance.
Rate of change of speed (m/s²). Constant gradient on a speed-time graph means uniform acceleration.
Negative acceleration — speed is decreasing over time. Shown as a downward-sloping segment on a speed-time graph.
On a distance-time graph: horizontal line (no distance covered). On a speed-time graph: zero speed segment.
The traps other students keep falling into on travel graphs questions — taken from recent Cambridge IGCSE 0580 examiner reports and mark schemes — and how to avoid them.
0580 Extended — recurring
Why it happens
Both have time on the horizontal axis; students forget which y-axis they're reading.
How to avoid it
Always check the y-axis label. Distance-time → gradient is speed. Speed-time → gradient is acceleration, area is distance.
Why it happens
Students focus on the moving sections.
How to avoid it
Average speed uses total distance over total time, including stops.
Why it happens
Reading off a graph in km/h then computing area in seconds.
How to avoid it
Convert units BEFORE doing the calculation. m/s ↔ km/h: multiply or divide by 3.6.
Why it happens
Treating an acceleration phase as constant speed.
How to avoid it
If the graph is sloped, the region is a triangle or trapezium — use the proper formula.
The things students keep getting wrong in this sub-topic, answered.