Jack drives a distance of 1 kilometer at 14 km/h. Then Jack drives an additional distance of 1 kilometer at 38 km/h. What is our average speed?
I don't understand how to solve this...
I don't understand how to solve this...
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Average speed is total distance traveled divided by the time spent. In the first segment, Jack travels 1 km for a time of (1 km) / (14 km/hr) = (1/14) hr. In the second segment, Jack travels 1 km for a time of (1 km) / (38 km/hr) = (1/38) hr.
So Jack has traveled a total of 2 km in (1/14) hr + (1/38) hr = 0.098 hr.
The average speed, then, must be 2 km / 0.098 hr = 20.5 km/hr.
Note, in my experience, it is very tempting for students to just average the 14 km/hr and the 38 km/hr and get 26 km/hr. You'll really want to avoid this temptation :) Jack spends more time traveling at 14 km/hr, so his average speed must be less than just the average of the speeds.
So Jack has traveled a total of 2 km in (1/14) hr + (1/38) hr = 0.098 hr.
The average speed, then, must be 2 km / 0.098 hr = 20.5 km/hr.
Note, in my experience, it is very tempting for students to just average the 14 km/hr and the 38 km/hr and get 26 km/hr. You'll really want to avoid this temptation :) Jack spends more time traveling at 14 km/hr, so his average speed must be less than just the average of the speeds.