SOLUTION: Please help me to solve this question!! : one third of a certain journey was covered at the speed of 20 km per hour , one fourth at the rate of 30 km per hour and the rest at th

Question 1189258: Please help me to solve this question!!
: one third of a certain journey was covered at the speed of 20 km per hour , one fourth at the rate of 30 km per hour and the rest at the rate of 50 km per hour.
Find the average speed ( per hour ) of the whole journey ?
Found 3 solutions by josgarithmetic, Solver92311, ikleyn:
Answer by josgarithmetic(39618)   (Show Source): You can put this solution on YOUR website!

, the rest at 50 kilom per hr

SPEEDS TIME DISTANCE PART1 20 (d/3)(1/20) d/3 PART2 30 (d/4)(1/30) d/4 PART3 50 (5d/12)(1/50) (5/12)d SUM d

total distance, d
total time,

AVERAGE SPEED,

-

Answer by Solver92311(821)   (Show Source): You can put this solution on YOUR website!

Let represent the total time of the trip and represent the total distance traveled. The average speed is equal to

There are three parts of this trip, so let the three distances be represented by ,, and and we know that

Also, if we have accounted for one-third of the trip and one-fourth of the trip, the rest of the trip must amount to:

So

But the average speed is the total distance divided by the total time, , so:

You can do your own arithmetic.

John

My calculator said it, I believe it, that settles it

From
I > Ø

Answer by ikleyn(52794)   (Show Source): You can put this solution on YOUR website!
.
one third of a certain journey was covered at the speed of 20 km per hour ,
one fourth at the rate of 30 km per hour and the rest at the rate of 50 km per hour.
Find the average speed ( per hour ) of the whole journey ?
~~~~~~~~~~~~~~~~

            Calculations by @josgarithmetic have FATAL ERRORS,
            so I came to bring a correct solution.

Let d be the distance. Part was covered at 20 km/h; it took = hours. Part was covered at 30 km/h; it took = hours. The rest distance, = kilometers, was covered at 50 km/h; it took = hours. Total time is = = = . Therefore, the average speed = = 30 km/h. ANSWER.

Solved.

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Do not accept any other answer.

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