Graphs 3
4 marks · HardOlivia walks from her home to the post office and back. Her journey is shown on this distance–time graph.
a) Work out Olivia's speed on her journey from home to the post office.
b) Explain why Olivia takes more time to return home compared to her outward journey.
Outward journey speed:
Reason for increased return time:
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Speed = 1.3 km / 8 min = 0.1625 km/min = 9.75 km/h
(b) The return journey takes longer because the graph's slope is less steep, showing Olivia walks more slowly coming back, possibly because she is tired or carrying something.
Common mistakes: Mixing up time intervals; Wrong units for speed; Not comparing gradients between outward and return journeys
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly finds distance and time for the outward journey (1.3 km in 8 min).
A1 (a) · 1 mark · Correctly calculates speed (accept answers between 9.5 and 10 km/h). Correct answer with consistent units.
B1 (b) · 1 mark · Identifies that the return journey has a less steep slope.
B1 (b) · 1 mark · Provides an explanation related to walking slower, being tired, or similar reasonable explanation.
Worked solution
a) Outward journey: Distance = 1.3 km, Time = 8 min
Convert to km/h: 0.1625 km/min × 60 = 9.75 km/h
b) The return journey (from 20 to 32 min) covers 1.3 km in 12 min, so the speed is lower. The flatter slope on the graph shows Olivia walks back more slowly, possibly due to tiredness or carrying a parcel.