we had to go 30km through the city and then 30km through the country.Through the city we averaged 40km/h and through the country we averaged 60km/h.What was our average speed for the entire journey ?
Speed= distance/time. At 40km/h you will take 3/4 hours to do 30km. At 60 km you will take 1/2 hours. So, the total time is 3/4 + 1/2 = 1 and 1/4. Hence you will travel 60km in 1 and 1/4 hours => average speed = 6/1 and 1/4= 60x4/5 = 48km.
So, the answer to the question is 48 km/h, not 50km/h. Many people make the same mistake of 50km/h, so don’t worry, you’re not alone if you think so.
To find the average speed for the entire journey, we need to calculate the total distance traveled and divide it by the total time taken.
First, let's calculate the time taken to travel through the city. We can use the formula time = distance / speed, where the distance is 30 km and the speed is 40 km/h. So, the time taken through the city is:
Time through city = 30 km / 40 km/h = 0.75 hours
Next, let's calculate the time taken to travel through the country. Using the same formula, the time taken through the country is:
Time through country = 30 km / 60 km/h = 0.5 hours
Now, to calculate the total time taken for the entire journey, we add the time taken through the city and the time taken through the country:
Total time = Time through city + Time through country = 0.75 hours + 0.5 hours = 1.25 hours
Finally, to find the average speed for the entire journey, we divide the total distance (60 km) by the total time (1.25 hours):
Average speed = Total distance / Total time = 60 km / 1.25 hours = 48 km/h
Therefore, the average speed for the entire journey is 48 km/h.