SOLUTION: If Alexandra increases her usual driving speed by 15km/hr, it will take her 2 hours less than her normal time to make a trip to her grandparents' house. If she decreases fer usual

Question 49919: If Alexandra increases her usual driving speed by 15km/hr, it will take her 2 hours less than her normal time to make a trip to her grandparents' house. If she decreases fer usual speed by 15km/hr, it will take her 3 hours more than her normal time to maked the trip. Can you determine how far she lives form her grandparents? Find a possible answer by counstructing a set of consistent values for time, distance and rate to solve.
Answer by Paul(988) (Show Source): You can put this solution on YOUR website!
Pretty confusing problem.
So we have 3 unknows; however, we only have 2 clues.
now we know that distance = speed * time
Let x be the speed, d be the distance and y be the time
EQUATION 1:

EQUATION 2:
If Alexandra increases her usual driving speed by 15km/hr, it will take her 2 hours less than her normal time to make a trip to her grandparents' house

D=(y-2)(x+15)
Subsitute for D:
xy=xy+15y-2x-30
2x=15y-30
x=7.5y-15 (subsitution no. 2)

EQUATION 3:
If she decreases fer usual speed by 15km/hr, it will take her 3 hours more than her normal time to maked the trip

D=(x-15)(y+3)
xy=xy-45-15y+3x
45=3x-15y
Subsitute for x:
45=3(7.5y-15)-15y
45+45=22.5y-15y
7.5y=90
y=12

(SPEED)7.5(12)-15=75 kmph
DISTANCE = 75*12=900 km
Hence, the distance from her house to her grandma's house is 900 km.
Paul.
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