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A girl is preparing for her first marathon by running on a straight road. She uses a smartwatch to calculate her running speed at different intervals. The graph (Fig. 4.31) depicts her velocity versus time. Estimate the distance she ran based on the graph.
Show Answer
Distance = area under the velocity-time graph (velocity in km h⁻¹, time in h, so area is in km).
Estimating Fig. 4.31 (rises to about 7.5 km h⁻¹ by 2 h, holds, then eases to about 6.5 km h⁻¹ by 6 h), the average speed is roughly 6.5–7 km h⁻¹ over 6 h, giving a distance of about 40 km . Count the grid squares under the curve on your copy of Fig. 4.31 for a precise value.
