It took Ellen 6 hours to ride her bike a total distance of 120 miles. For the first part of the trip, her speed was constantly 25 miles per hour. For the second part of her trip, her speed was constantly 15 miles per hour. For how many miles did Ellen travel at 25 miles per hour
She travelled 75 miles at 25 miles per hour, since 3x25miles+3x15miles=120 miles in 6 hours.
You can create 2 equations
t1 = time taken for for first part of travel
t2 = time taken for 2nd part of travel
t1 + t2 = 6… 1st equation
Now, distance = speedtime
Therefore,
25t1 + 15t2 = 120 …2nd equation
solve both, you will get t1 = 3,
Thus distance travelled for second part = t1speed1 = 3*25 = 75 miles
We can just assume the time for first and 2nd part to be 3 hours each, right ?
I am not sure that we can assume that!!
This is right answer:)
Thanks
For the first 5 hours of a trip, a plane averaged 120 kilometers per hour. For the remainder of the trip, the plane travelled an average speed of 180 kilometers per hour. If the average speed for the entire trip was 170 kilometers per hour, how many hours long was the entire trip.
How about this one!! I am really struggling with these!!
that’s a wheighted average problem. If the total average speed is 170, you can conclude that the ratio of hours at 120 kph to hours at 180 kph is 1:5. Since5 hours were spent at 120kph, thus 25 hours were spent at 180 kph.
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You cannot since the question doesn’t say so
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yes you right , we cant assume.
is there any other way to solve this one too!!