Question

A part of a journey is covered in $1$ hour $40$ minutes at $75$ km/hr and the remaining part of it is covered in $2$ hours $50$ minutes at $60$ km/hr. Find the average speed during the whole journey.

• A. $36\frac{3}{7}$ km/hr
• B. $65\frac{5}{9}$ km/hr
• C. $86\frac{4}{3}$ km/hr
• D. $23\frac{4}{7}$ km/hr

Answer 1

Answer: (B)

$65\frac{5}{9}$ km/hr

Total Distance covered $=$ Distance covered in $\frac{5}{3}$ hour at $75$ km/hr $+$ Distance Covered in $\frac{17}{6}$ hour at $60$ km/hr

Distance covered in $\frac{5}{3}$ hour at $75$ km/hr $=\frac{5}{3}\times 75=125$ km

Distance Covered in $\frac{17}{6}$ hour at $60$ km/hr $=\frac{17}{6}\times 60=170$ km

Total time of journey $\frac{5}{3}+\frac{17}{6}=\frac{9}{2}$ hours

Average speed $=\frac{\text{Total Distance}}{\text{Total Time Taken}}$

$=\frac{125+170}{\frac{9}{2}}=295\times \frac{2}{9}=\frac{590}{9}=65\frac{5}{9}$

Hence, option B.