SOLUTION: I have been given a very challenging word problem and cannot figure it out. It's on Finding rates. Jeff bicycles 160 miles at the rate of r mph. The same trip would have taken 2

Question 742968: I have been given a very challenging word problem and cannot figure it out. It's on Finding rates. Jeff bicycles 160 miles at the rate of r mph. The same trip would have taken 2 hours longer if he had decreased his speed by 4 mph. Find r. Can you please help me solve this problem?...thanks
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
d=160
speed = r
t=160/r

d=160
new speed = r-4
t= 160/(r-4)

time new speed time original speed = 2

multiply by r(r-2)
160r-9600+160r= 2r(r-4)

320r-9600=2r^2-8r
2r^2-328r+9600=0
/2
r^2-164r+4800=0
r^2-164r+6724=6724-4800
(r-82)^2=1924
r-82=43.86
r=82-43.86
r=38.14
RELATED QUESTIONS
i have been working on this problem for an hour and cannot seem to figure it out. Thank... (answered by Fombitz,edjones)

I would really appreciate any help I could get on this question. Word problems are sooo... (answered by ankor@dixie-net.com)

Karen�s boat has a top speed of 10 miles per hour in still water. While traveling on a... (answered by josmiceli)

a lab needs to make 100 gallons of an 18% acis solution by mixing a 12% acid solition... (answered by josmiceli)

It is the year 2074 and the electric truck is a reality. Jeff is an independent truck... (answered by scott8148)

Graph the inequality. 2x + 3y > 6 I have been having the hardest time with this... (answered by stanbon)

Could you please help me with this word problem. I have been really trying to figure it... (answered by ankor@dixie-net.com)

Please help me solve this word problem: It takes a freight train 2 hours more to travel... (answered by sudhanshu_kmr)

I have been working on this problem for awhile now and I still can't figure it out. I was (answered by ankor@dixie-net.com)