At a game of billiards, A can give B 15 points in 60 and A can give C to 20 points in 60. How many points can B give C in a game of 90?
Answer: C
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.
\[ A\,60 : B\,45, \qquad A\,60 : C\,40 \]
\[ B : C = 45 : 40 \]
In a game of 90, when B scores 90:
\[ C = 90 \times \frac{40}{45} = 80 \]
\[ \text{B can give C} = 90 - 80 = 10 \text{ points} \]
Both handicaps are quoted against the same A total, which is what lets B and C be compared without ever finding a speed.
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