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Algebra Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

Jaina is a train driver. She drives the train from Sao Paolo to Rio. The journey usually takes 4 hours, non-stop and at constant speed. One day, the train stopped half way for 40 minutes. By what percentage did Jaina then need to increase the train's speed to still arrive on time?

(A) $30$ (B) $40$ (C) $50$ (D) $60$ (E) $70$

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