tianzhu:Michaelia0816:Also this one, help!
The ratio of the average speed of Ali, Ben and Carl was 2:3:4 respectively. They started driving at the same time and after 5h, they had covered a total of 675 km. What was the average speed of Ben?
Hi
A:B:C --------2:3:4(Speed)
A:B:C --------2:3:4(Distance)
A:B:C --------4:3:2(Time)
Distance varies in direct proportion to speed.
Time is inverse proportion to speed.
9 units -------- 675
1 unit ------- 75
Ben -------- 3*75 ------- 225 km
For time, 9 units ------- 300 minutes
3 units ------- 100 mins or 5/3h
Average speed of Ben ------- 225/5/3 --------- 135 km/h
Best wishes
Hi Tianzhu, I noticed you did not use the '5 hr' in the working and if the average speed of Ben is 135km/h, then after 5 hr, the distance travelled by Ben is 675km. But 675km is the distance covered by the 3 men.