Answer:
The original speed of the grey wolf can be 9 and/or 48 km/hour
Step-by-step explanation:
There are two trips. One to King Castle (KC) to Magic Apple Garden (MAG), and then back (MAG - KC).
First trip: KC - MAG
It takes the same distance as MAG - KC so distance can be D for both.
Then it is stated that it takes 5 hours or 300mins for him to go from KC - MAG, and the speed is constant.
Let x be speed.
So the equation for this is:
D=5x
Second trip: MAG - KC
Here he goes 36 mi at constant speed (x), then picks up his speed by 3 km/hour (x+3).
For Time:
He reaches to KC, 15 mins earlier than KC - MAG, so he reaches there in 4.75 hours or in 275 min.
The problem splits into two as there are two different times, for the two parts of the journey or distance for MAG - KC.
Let T#1 = a, and T#2 = b.
Let D#2 = D-36
The equation for a:
a = 36/x --> This is he is at a constant speed and went for 36mi.
Next:
The equation for b:
b = (x+3)/D#2
These two equation have to be added as (a+b) = 4.75 --> 4.75 is the total time for MAG - KC.
So the equation is:
36/x + (5x-36)/x+3 = 4.75 --> Knowing (a+b) = 4.75, just put 4.75 as the equal, and add the fractions that equal (a) and (b).
Now Solve:
36/x + (5x-36)/x+3 = 4.75
0.25s^2 + 108 + 5s^2 - 36s = 4.75s*(s+3)
0.25s^2 - 14.25s + 108 = 0
(14.25 +- Square root (203.06 - 108))/0.5
(14.25 +- Square root (95.0625))/0.5
(14.25 +- 9.75)/0.5
Answer:
s = 9, s=48.
Therefore the original speed of the grey wolf can be 9 and/or 48 km/hour.
