Question

please help
A freight train completes its journey of 150 miles 1 hour earlier if its original speed is increased by 5 miles/hour. What is the train’s original speed?

a. 20 miles/hour
b. 25 miles/hour
c. 30 miles/hour
d. 35 miles/hour

Answer 1

You can use the equation
distance = rate * time

Answer 2

A freight train completes its journey of 150 miles 1 hour earlier if its original speed is increased by 5 miles/hour. What is the train's original speed?

We have two equations

150 = r*t
150 = ( r + 5) ( t - 1)

Answer 3

how would I figure those out..? the r & t?

Answer 4

you can solve this system by substitution.
In the first equation solve for t in terms of r
150/r = t

Answer 5

plug that into the second equation for t

Answer 6

yeah... that confuses me...

Answer 7

150 = r*t
Solve for t
t = 150/r

substitute into second equation

150 = ( r + 5) ( 150/r - 1)

distribute and simplify

Answer 8

150 = r*150/r + 5*150/r - r - 5

150 = 150 + 5*150/r - r - 5
0 = 750 / r - r - 5

Answer 9

multiply both sides by r
0 = 750 - r^2 - 5r

Answer 10

then factor (or use quadratic formula)

Answer 11

( r - 25 ) ( r + 30 ) = 0

r = 25 , - 30

we reject the negative solution