Discussion

A can run 20 m while B runs 25 m. In a km race, B beats A by:

Answer: B

In these problems the two runners are compared by the distances they cover in the same time, so their speeds are in the ratio of those distances.

\[ A : B = 20 : 25 \]

In a 1000 m race B finishes first, and in that time A covers

\[ 1000 \times \frac{20}{25} = 800 \text{ m} \]

\[ \text{B beats A by } 1000 - 800 = 200 \text{ m} \]

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