Question : A train travels at a speed of 18 m/s in the first 5 minutes, covers 7.5 km in the next 10 minutes and covers 12 km in another 10 minutes. What is its average speed (in km/h, rounded off to 1 decimal place) for the entire journey?
Option 1: 59.8
Option 2: 71.2
Option 3: 45.7
Option 4: 64.6
Correct Answer: 59.8
Solution :
Speed of train in the first 5 minutes = 18 m/s
Distance travelled by train in next 10 mins = 7.5 km
Distance travelled by train in next 10 mins = 12 km
Distance = Speed $\times$ Time
Distance travelled by train in the first 5 mins = $18\times (5\times 60)$ = 5400 m = 5.4 km
Total time taken = $\frac{5}{60} + \frac{10}{60} + \frac{10}{60} = \frac{25}{60} = \frac{5}{12}$ hr
Average Speed = $\frac{\text{Total distance}}{\text{Total time taken}}$
$= \frac{(5.4 + 7.5 + 12)\times 12}{5} = \frac{24.9\times 12}{5}=\frac{298.8}{5} = 59.8$ km/hr
Hence, the correct answer is 59.8.
Related Questions
Know More about
Staff Selection Commission Combined Grad ...
Result | Eligibility | Application | Selection Process | Preparation Tips | Admit Card | Answer Key
Get Updates Brochure
Your Staff Selection Commission Combined Graduate Level Exam brochure has been successfully mailed to your registered email id “”.
