A) 20 kmph
B) 25 kmph
C) 30 kmph
D) 40 kmph
Correct Answer: A
Solution :
Starting \[\therefore \] Total distance \[=3\times 4\] \[=12\,km\] Total time \[=\frac{\text{Distance}}{Speed}\] \[=\left( \frac{3}{10}+\frac{3}{20}+\frac{3}{30}+\frac{3}{60} \right)\] hours \[=3\left( \frac{1}{10}+\frac{1}{20}+\frac{1}{30}+\frac{1}{60} \right)\] hours \[=3\left( \frac{6+3+2+1}{60} \right)\] \[=3\times \frac{12}{60}=\frac{3}{5}\] hours \[\therefore \] Required speed \[=\frac{Total\text{ }distance}{~Total\text{ }time}\] \[=\frac{12}{\frac{3}{5}}=\frac{12\times 5}{3}\] \[=20\text{ }kmph\]You need to login to perform this action.
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