Discussion

A is 2 1/3 times as fast as B. If A gives B a start of 80 m, how long should the race course be so that both of them reach at the same time?

Answer: C

A is \( 2\tfrac{1}{3} = \tfrac{7}{3} \) times as fast as B, and B starts 80 m ahead. Let the course be \( d \) metres.

\[ \frac{d}{7/3} = \frac{d - 80}{1} \]

\[ 3d = 7d - 560 \quad\Longrightarrow\quad 4d = 560 \]

\[ d = 140 \text{ m} \]

Checking: A runs 140 m while B runs 60, and \( \tfrac{140}{60} = \tfrac{7}{3} \).

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