CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon


Question

A boy runs for 10 minutes at a speed of 18km hr. At what speed should he run for the next 20 minutes so that the average speed becomes 12 km hr


Solution

Average speed (12km/hr) = Total Distance / Total Time
                         D1 + D2 / T1 + T2
Total Time = 10 min + 20 min = 30 min = 1/2 Hour
D1 = Speed * Time = 18* 1/6 (10 min = 1/6 hr)
= 3km 
D2 = ?
12 = 3 + D2 / 1/2
12 * 1/2 = 3 + D2
6 = 3 + D2
6 - 3= D2
3 km = D2
Speed = Distance / Time
           = 3/ 1/3 (20 min = 1/3 hr)
           = 3 * 3 (Reciprocal)
           = 9 km/hr

 

Physics

Suggest Corrections
thumbs-up
 
0


similar_icon
Similar questions
View More


similar_icon
People also searched for
View More



footer-image