Question

I tried working this problem out and I know someone tried to help me earlier but I just dont understand it HELP!!

Rusty has a boat goes 12 mi. an hour. Find the current speed of the river if he can go 3 mi. upstream in the same time as he goes 5 mi. downstream.

Answer 1

ok, distance= rate * time right?

Answer 2

yes, but it asks to find the current speed...so where does that come in to play?

Answer 3

I am not good with word problems at all :(

Answer 4

ok, well my rate upstream is 12-x
and downstream is 12+ x
where x is my speed of current

Answer 5

solve for time in the first equation i gave you and you have
distance/rate= time

Answer 6

you know that the time for going upstream 3 miles, is equal to going to downstream 5 miles

Answer 7

so, 3/(12-x)=5(x+12)

now just solve for x

Answer 8

ok, im working on it lol ill get back to you on this one

Answer 9

I got the current speed to be 12 miles per hour....is this correct?

Answer 10

no,

Answer 11

:(

Answer 12

i suck at this

Answer 13

what did you do to solve for x?

Answer 14

one second, i think i know what i did wrong

Answer 15

oh wow i am totally lost :(

first i multiplied both sides by 12 -x and i got

36 - 3x = 60 - 5x / x + 12

is this right so far?

Answer 16

multiply both sides by the lcd of both fractions

Answer 17

yes now multiply by x +12

Answer 18

wait no its wrong

Answer 19

when multiplying 36 - 3x by x + 12 do I use the foil method?

Answer 20

:(

Answer 21

its not 35-3x! because qhen you multiply x-12 to both sides, it cancels on the left side

Answer 22

(x-12) * (3/12 -x)....the denominator cancels out but you still have to multiply 3 by x-12

Answer 23

no! thats the whole point of multiplying by x-12 so they cancel,

see when you multiply you will have

3(x-12)/(x-12) now, the x-12 cancel out and you only have left

Answer 24

3

Answer 25

OMG!! I hate word problems......................

Answer 26

it's not the word problem, you need to practice your algebra...

Answer 27

no, i always have trouble with word problems. i know how to do algebra, but you dont understand...i have been working non stop on this home work assignment for 3 days straight....i am TIRED and my brain hurts....and word problems get me so confused that i make stupid mistakes in my algebra

Answer 28

yeah, i know im a tutor and i help out people, and i know how it stresses people

Answer 29

ok so if it cancels out and leaves 3 then you would end up with

3 = 5 / x + 12

correct?

Answer 30

yeah not multiply both sides by x+12

Answer 31

3x + 36 = 5 ???

Answer 32

umm multiply the x-12 to the 5 on the right side

Answer 33

it does not cancelt out in the right since the denominator of the right side is x+12

Answer 34

3 = 5x - 60 /x + 12

Answer 35

48 miles per hour!!!!!!

Answer 36

please tell me i am right

Answer 37

wait lol i havent done the work yet give me a minute

Answer 38

lol

Answer 39

yep!

Answer 40

YAY!! Thank you so much for helping me and not giving up on me!!!

You are the best!!

Answer 41

no problem i love math!

Answer 42

i do too but i hate word problems lol

Answer 43

whats the use of math if we can't apply it to the world?

Answer 44

that is a very good point :)

Answer 45

I have ran into a big problem with this question. When I do this equation

3 / x-12 = 5 / x+12

x turns out to equal 48.

But then if you do the equation this way:

3 / 12 - x = 5 / 12+x

x turns out to equal 3

So which way is correct?