CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

A boy runs for 10 min at a uniform speed of 9 km/h. At what speed should be run for the next 20 min, so that the average speed comes to 12 km/h?

A
10.5 km/h
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
12.5 km/h
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
13.5 km/h
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
11.5 km/h
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is C 13.5 km/h
Total time of travel =10 min+20 min=30 min
The average speed is 12 kmph
Using s=vt, the total distance covered in 30 min with given average speed is 12 kmph×30 min=12kmh×12h=6 km.
The distance covered in the first 10 min is
9 kmph×10 min=9kmh×16h=1.5 km
Thus, he has to cover 6 km1.5 km=4.5 km in the next 20 min.
The speed required is
4.5 km20 min=4.5 km(2060)h=13.5 kmph.

flag
Suggest Corrections
thumbs-up
5
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Average speed
PHYSICS
Watch in App
Join BYJU'S Learning Program
CrossIcon