question_answer

A man travels from A to B at speed of \[27\text{ }km/hr\] in 37 minute and he travels a distance from B to C with speed of \[37\text{ }km/hr\] in 37 minute. Find the average speed of whole journey.

A)  \[28\text{ }km/hr.\]                   

B)  \[30\text{ }km/hr.\]

C)  \[32\text{ }km/hr.\]                   

D)  \[36\text{ }km/hr.\]

Correct Answer: C

Solution :

Total distance between A and B \[=Speed\times Time=27\times \frac{37}{60}=\frac{27\times 37}{60}km\] Distance between B to C \[=\,\,Speed\times Time=37\times \frac{37}{60}\] \[=\frac{37\times 37}{60}km\] \[\therefore \]  Total distance travelled by man \[=\frac{27\times 37}{60}+\frac{37\times 37}{60}=\frac{37}{60}\,(27+37)\] \[=\frac{592}{15}\,km\] Total time taken \[=37+37=74\]minute \[\therefore \] Average speed \[=\frac{Total\text{ }Distance}{Total\,\,time}\]             \[=\frac{592}{15}\div \frac{74}{60}=\underline{\mathbf{32}\,\mathbf{km/h}}\]