Question

Mary drove 4 hours to reach her camping spot. She increased her speed by 15 miles per hour reducing her travel time by one hour. How fast did she drive going to the camping spot?

Answer 1

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