Stretching a Ruler. In this illustration, the ruler at top is normal sized, and has ants drawn at 2, 4, 7 and 12 cm. The same ruler is drawn below, but stretched to twice its length. The ants are still at their positions as above, but the ant at 2 cm sees the ant at 4 cm move away at 2 cm/min, the ant at 7 cm move away at 5 cm/min and the ant at 12 cm move away at 10 cm/min.
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