SOLUTION: a man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 kms of the journey in 5 hrs.what is the average speed for the whole journey?
a. 7 km/hr
b. 5 9/11
Algebra.Com
Question 880185: a man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 kms of the journey in 5 hrs.what is the average speed for the whole journey?
a. 7 km/hr
b. 5 9/11 km/hr
c. 8 km/hr
d. 7 1/2 km/hr
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
a man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 kms of the journey in 5 hrs.
what is the average speed for the whole journey?
:
let a = his average speed for the whole journey
Write a time equation time = dist/speed
:
+ 5 =
add the distances, multiply equation by 6a, cancel the denominators & you have:
30a + 6a(5) = 6(70)
30a + 30a = 420
60a = 420
a = 420/60
a = 7 km/hr is the av speed
:
:
Confirm this find the time at 6 km/hr
30/6 = 5 hrs for total 10 hrs
70/10 = 7 km/hr
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