Arun covers first 28 kms of his journey in 45 minutes and the remaining 32 kms in 35 minutes. What is his average speed in m/s?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(\displaystyle 12\frac{1}{2}\)
Average speed is the total distance divided by the total time, not the average of the two speeds.
Total distance: \(28+32=60\) km
Total time: \(45+35=80\) minutes \(=\displaystyle\frac{4}{3}\) h
Average speed: \(60\div\displaystyle\frac{4}{3}=45\) km/h
In m/s: \(45\times\displaystyle\frac{5}{18}=12.5=12\frac{1}{2}\) m/s