Question
If a person walks at (2/3) of his
normal speed, he arrives at his office 30 minutes late. What is the usual time taken by him to reach his office?Solution
ATQ,
Let the distance covered by the person to reach the office be 'd' meters, the usual time taken be 't' minutes, and the usual speed be 's' meters per minute. According to the question: 
3d=2s×(t+30)... (1) (d/s) = t So, d=s×t... (2) Using substitution from equation (2) into equation (1): 3st=2s×(t+30) Simplifying = 3st = 2st+60s Or, st=60s Thus, t = 60 Therefore, the usual time taken by the person to reach the office is 60 minutes.
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