Question : A man makes four trips of equal distances. His speed on the first trip was 720 km/hr and in each subsequent trip, his speed was half of the previous trip. What is the average speed of the man in these four trips?
Option 1: 104 km/hr
Option 2: 156 km/hr
Option 3: 192 km/hr
Option 4: 288 km/hr
New: SSC CHSL tier 1 answer key 2024 out | SSC CHSL 2024 Notification PDF
Recommended: How to crack SSC CHSL | SSC CHSL exam guide
Don't Miss: Month-wise Current Affairs | Upcoming government exams
New: Unlock 10% OFF on PTE Academic. Use Code: 'C360SPL10'
Correct Answer: 192 km/hr
Solution : A man makes four trips of equal distances. His speed on the first trip was 720 km/hr. In each subsequent trip, his speed was half of the previous trip. Let's denote the distance of each trip as d. For the first trip, his speed was 720 km/hr, so the time taken was = $\frac{\text{d}}{720}$ For the second trip, his speed was $\frac{720}{2}$ = 360 km/hr So the time taken was = $\frac{\text{d}}{360}$ For the third trip, his speed was $\frac{360}{2}$ = 180 km/hr So the time taken was = $\frac{\text{d}}{180}$ For the fourth trip, his speed was $\frac{180}{2}$ = 90 km/hr So the time taken was = $\frac{\text{d}}{90}$ So, the total distance travelled was 4d, and the total time taken was = $\frac{\text{d}}{720}$ + $\frac{\text{d}}{360}$ + $\frac{\text{d}}{180}$ + $\frac{\text{d}}{180}$ Average speed = $\frac{\text{Total distance}}{\text{Total time}}$ = $\frac{4\text{d}}{\frac{\text{d}}{720} + \frac{\text{d}}{360} + \frac{\text{d}}{180} + \frac{\text{d}}{180}}$ = $\frac{4}{ (\frac{1}{720} + \frac{2}{720} + \frac{4}{720} + \frac{8}{720})}$ = $\frac{4} {\frac{15}{720}}$ = $4 \times {\frac{720}{15}}$ = 192 km/hr Hence, the correct answer is 192 km/hr.
Candidates can download this e-book to give a boost to thier preparation.
Result | Eligibility | Application | Admit Card | Answer Key | Preparation Tips | Cutoff
Question : Rajinder drives his car at an average speed of 40 km/hr to cover half of his total distance and thereafter he increases his speed to 60 km/hr. He covers his journey in 7 hours. What is the average speed of Rajinder on this journey?
Question : A truck covers three equal distances of 100 km at the speeds of 200 km/hr, 300 km/hr, and 600 km/hr. Find the average speed of the truck for the whole journey.
Question : A bus travels for three hours at 60 km/hr, four hours at 50 km/hr, and the next five hours at 50 km/hr. Find its average speed.
Question : A train travelling from Mumbai to Goa covered the first 420 km at a speed of 60 km\hr and then covered the remaining 95 km at a speed of 65 km/hr. Find its average speed in km/hr.
Question : A man travelled a certain distance by train at the speed of 50 km/hr and walked back the same distance at the speed of 10 km/hr. If the whole journey took 12 hours, then what was the distance travelled by train?
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile