Question 1102271
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This is a good example of inverse variation: the faster you move, the less time it takes; the slower you move, the more time it takes.<br>
Ryan took 15 minutes to walk to school; his brother took 20 minutes.  The ratio of the times is 3:4.
Since the distance is the same for both of them, the ratio of the speeds is 4:3.<br>
So Ryan's brother's speed is 3/4 of Ryan's speed: {{{(3/4)*70 = 52.5}}}