Question

Jessie recently drove to visit her parents who live 240240 miles away. On her way there her average speed was 2525 miles per hour faster than on her way home (she ran into some bad weather). If Jessie spent a total of 88 hours driving, find the two rates.

Answer 1

Answer:

The speed/rate to her parent's house is x = 75 mph

The speed/rate from her parent's house is y = 50 mph

Step-by-step explanation:

Given;

Distance to her parent's house = 240 miles

Total distance travelled (to and fro) = 240×2 = 480 miles

Total time taken t = 8 hours

On her way there her average speed was 25 miles per hour faster than on her way home (she ran into some bad weather)

Let x and y represent her speed to and from her parent's house respectively.

x = y+25 ......1

The time taken to her parent's house is;

time = distance/velocity

t1 = 240/x = 240/(y+25)

The time taken from her parent's house is;

time = distance/velocity

t2 = 240/y

Total time taken t = t1 +t2

t = 240/(y+25) + 240/y = 8

Solving for y ;

(240y + 240(y+25))/(y^2 +25y) = 8

Cross multiply;

240y + 240y+6000 = 8y^2 + 200y

480y +6000 = 8y^2 + 200y

8y^2 + 200y -480y -6000 = 0

8y^2 - 280y - 6000 = 0

Divide through by 8;

y^2 - 35y - 750 = 0

Solving the quadratic equation;

y = 50

or

y = -15

Velocity cannot be negative, so y = 50mph

From equation 1;

x = y+25

Substituting y =50

x = 50 + 25

x = 75 mph

The speed/rate to her parent's house is x = 75 mph

The speed/rate from her parent's house is y = 50 mph