SOLUTION: Walking at 6/7th of his usual speed, a man is 25 mins too late. His usual time is

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Question 494811: Walking at 6/7th of his usual speed, a man is 25 mins too late. His usual time is
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
At his usual speed:
(1) +d+=+r%2At+
At his slower rate,
(2) +d+=+%286%2F7%29%2Ar%2A%28t+%2B+25%29+
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Substitute (1) into (2)
+r%2At+=+%286%2F7%29%2Ar%2A%28t+%2B+25%29+
+7r%2At+=+6%2Ar%2A%28t+%2B+25%29+
+7r%2At+=+6r%2At+%2B+150r+
Divide through by r
+7t+=+6t+%2B+150+
+t+=+150+
His usual time is +150+ min
or +150%2F60+ = 2 and 1/2 hours