SOLUTION: I am not sure how to set this equation up? I am really getting frustrated and all I need help with is understanding how to use the D=r(t) table to set this up. Here is the question

Algebra.Com
Question 359035: I am not sure how to set this equation up? I am really getting frustrated and all I need help with is understanding how to use the D=r(t) table to set this up. Here is the question:
Junior’s boat will go 15 miles per
hour in still water. If he can go 12 miles downstream in the
same amount of time as it takes to go 9 miles upstream,
then what is the speed of the current?
Here is what I have so far:
D R T
12mile 15mph = 3/5 hr
9miles 15mph = 4/5 hr
Is this correct or am I making an error somewhere is setting this up?
Found 2 solutions by mananth, ewatrrr:
Answer by mananth(16946)   (Show Source): You can put this solution on YOUR website!
Junior’s boat will go 15 miles per
hour in still water. If he can go 12 miles downstream in the
same amount of time as it takes to go 9 miles upstream,
then what is the speed of the current?
...
current speed =xmph
downstream speed = x+15
upstream speed = 15-x
..
downstream distance = 12 miles
time downstream = 12/x+15
..
upstream distance = 9 miles
upstream time = 9/15-x
..
these times are same
12/(x+15)=9/(15-x)
12(15-x)=9(x+15)
180-12x=9x+135
-12x-9x=135-180
-21x=-45
/-21
x=45/21
x= 2.14 mph speed of current
m.ananth@hotmail.ca
Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!


Hi,

distance formula: d = rt   t = d/r

Letting c be the rate of the current

12 miles downstream in the 'same amount of time' as it takes to go 9 miles upstream



Cross multiplying to solve for c

12(15 -c ) = 9(15+c)

12*15mph - 9*15mph = 2c

45 = 2c

22.5mph= c 

RELATED QUESTIONS


I need help with this problem. I'm not understanding what it is I should do.

Write the  (answered by stanbon,bucky)

Susan is six years older than Mary. She is also twice as old as Mary was when Susan was... (answered by solver91311)

I am trying to solve in the simplest form

{{{(y-2)/(y+3)}}} - {{{y/(2y+6)}}} 
I am... (answered by scianci)

I am currently working on evaluation exponential function I know how to plug in the... (answered by richwmiller)

I am getting really frustrated because I don't know how to go about solving this at all.... (answered by venugopalramana)

Can you please help me to solve this equation. I have tried but am getting frustrated. I... (answered by lwsshak3)

I wasn't sure where to put this because my text is Inequalities, Permutations, and... (answered by longjonsilver)

I am not understanding I am on section 3.4 in math 105, my question is 2x+5y is greater... (answered by josgarithmetic)

1.1(2.6)^2x = 6(4.4)^x

I have to solve for x and I need the exact solution, not a... (answered by rapaljer)