Answer:
45 miles per hour
Step-by-step explanation:
Mary drove 4 hours to reach her camping spot. Driving home, she increased her speed by 15 miles per hour, reducing her travel time by 1 hour. How fast did she drive going to the camping spot?
d = rt
Where,
d = distance
r = rate of speed
t = time
Going to the camping spot
d=rt
Where, t = 4 hours
d = r × 4
d = 4r (1)
Driving home
She reduced her travel time by 1 hour
That is t = 4 -1 = 3 hours
Then increased speed by 15 miles per hour
That is r = r + 15
d=rt
d = (r+15) × 3
d = 3r + 45 (2)
Equating the two equations
4r = 3r + 45
Collecting like terms
4r - 3r = 45
r = 45
r = 45 miles per hour
check:
d = 4r
d = 45*4
=180 miles
d = 3r + 45
d = 3*45 + 45
= 135 + 45
=180 miles
