SOLUTION: a motorist travels for one hour at an average speed of 72 km/h and then for two hours at an average speed of 90 km/h. Calculate his average speed for the whole journey

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Question 672306: a motorist travels for one hour at an average speed of 72 km/h and then for two hours at an average speed of 90 km/h. Calculate his average speed for the whole journey
Found 2 solutions by Alan3354, sachi:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
a motorist travels for one hour at an average speed of 72 km/h and then for two hours at an average speed of 90 km/h. Calculate his average speed for the whole journey
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Use d = r*t to get the total distance
Divide by the total time to get the average speed

Answer by sachi(548) About Me  (Show Source):
You can put this solution on YOUR website!
journey speed(km/hr) hrs distance(km)=speed*hrs
1st 72 1 72
2nd 90 2 180
total 3 252
so the average speed for the whole journey=252/3=84 km/hr
ans