5th Class Mathematics Arithmetic Question Bank Arithmetic

  • question_answer A man covers a certain distances between his house and office on scooter. With an average speed of 30 km/hr, he is late by 10 min., however, with a speed 40 km/hr, he reaches his office 5 min earlier. Find the distance between his house and the office.

    A)  20 km             

    B)  10 km

    C)  15 km             

    D)  30 km

    Correct Answer: D

    Solution :

     Let distance be \[x\] km. Time taken to cover \[x\] km at 30 km/hr. \[=\frac{x}{30}hrs\] Time taken to cover x km at 40 km/hr. \[=\frac{x}{40}hrs\] Difference between the time taken \[=15\min =\frac{1}{4}hr\] \[\therefore \frac{x}{30}-\frac{x}{40}=\frac{1}{4}\] \[\frac{40x-30x}{1200}=\frac{1}{4}\] \[\frac{10x}{1200}=\frac{1}{4}\] \[x=\frac{1200}{4\times 10}=30\]

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