Calculating Avg Speed of Round Trip: What's Wrong?

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Homework Help Overview

The problem involves calculating the average speed of a round trip, where the first segment is traveled at 90 km/h, followed by a one-hour break, and the second segment at 50 km/h. The original poster is attempting to reconcile their calculations with the expected average speed of 55 km/h.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster calculates the time for each segment of the trip and attempts to find the average speed but questions their method. Participants discuss the importance of considering total time, including breaks, in the average speed calculation.

Discussion Status

Some participants have provided clarifications regarding the calculation of total time and distance. The discussion is evolving as participants reflect on the implications of including the break in their calculations.

Contextual Notes

There is a focus on understanding how breaks affect average speed calculations, and participants are exploring the assumptions made in the original poster's approach.

camboguy
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ok here's the question then what i did so far.

Q> calculate the avg speed of a complete round trip in which the first 200km is covered at 90km/hr, followed by a one-hour lunch break, and final 200km is covered at 50km/hr.


What i tried> 200km/90kmphr then i got 2.2hr and then 200/2.2hr to get the avg speed, which was 90km.

then i did 200km/50kmphr then i got 4hr and then 200km/4hr and got 50km. then avg those speeds but i keep geting around 70 and the answer is supposed to be 55km/hr.

what am i doing wrong?
 
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"and then 200/2.2hr to get the avg speed, which was 90km."

but you are missing first half with the second half?

average speed = total distance travelled/total time

so total dist = 400
and total time =2.2+4+1
 
aaaa i see thank you
 
ohh.. now I got it, what you were doing there.. "200/2.2"
I think it would have worked if they hadn't stopped for the break
 

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