Graphs 3

2 marks · Easy

A car is stationary for 30 minutes and then travels 12 km in 40 minutes at a constant speed. What is the speed of the car in km/h?

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18 km/h (±0.01)

Common mistakes: Dividing by total time including stopped time (70 min).; Calculating 12/70 × 60 = 10.3 km/h.

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Marking points

M1 · 1 mark · Divides distance by time while moving only (ignores stopped time): 12 km / 40 min.

A1 · 1 mark · Gives correct answer: 18 km/h.

Worked solution

Speed = Distance / Time = 12 km / (40/60) h = 12 / (2/3) = 18 km/h.