need some algebra help...

[ross]

i'm horrible with word problems and this is a take home quiz of 4 questions worth 100 points and i'm stuck on a problem.

heres the problem:

Mark's workout consists of jogging for 3 miles, and then riding his bike for 5 miles at a speed 4 miles per hour faster than he jogs. If his total workout time is 1 hour, find his jogging speed and his biking speed.

[John]

i think its 6 and 10.

jog 3 miles at 6 mph = 30 minutes

bike 5 miles at 10 mph = 30 minutes

that seems to fit everything. 60 minute workout, and bike speed is 4mph faster than running speed.

[ross]

haha thanks man i just got the same answer..now i just need to figure out how to show the work because i didn't figure it out "by the book" in the way the professor wants to see the work

[John]

running speed = x

bike speed = x+4

runs 3 miles/.5 hour = 6 mph

6mph + 4 mph= 10 mph

bikes 5 miles/.5 hour = 10 mph

???

[Kip Drordy]

i'm horrible with word problems and this is a take home quiz of 4 questions worth 100 points and i'm stuck on a problem.

heres the problem:

Mark's workout consists of jogging for 3 miles, and then riding his bike for 5 miles at a speed 4 miles per hour faster than he jogs. If his total workout time is 1 hour, find his jogging speed and his biking speed.

Are you still in elementary school?

[John]

not everyone is an asian math genius.

[ross]

Are you still in elementary school?

haha no...math 104 at columbus state. its intermediate algebra.

[BornSinner]

not everyone is an asian math genius.

DAMN!!!!

You beat me to it

[John]

you could write it like this maybe, where x is jogging and Y is biking

x mph * .5 hour = 3 miles

x = 3/.5

x = 6

------

y = (x+4)

y mph * .5 hour = 5 miles

y = 5/.5

y = 10

[ross]

the only issue i see is how do i prove that it takes .5 hr for each exercise? in the original problem it only says the total workout lasts 1 hr.

[Kip Drordy]

You don't

Running speed = x

Biking speed = x+4

x = miles/min

Time (60 min) = 3/x + 5/(x+4)

[yotaman88210]

You don't

Running speed = x

Biking speed = x+4

x = miles/min

Time (60 min) = 3/x + 5/(x+4)

[ross]

i fucking hate math

[Kip Drordy]

i fucking hate math

Yea, but it's like anything else, the more you practice the better you'll get. Did you solve it? I could give you the rest of the solution, but you'll be better off trying to figure it out yourself first.

Besides this is the kind of shit that you might have to use one day. Motor sports in general is very math intensive.

[ross]

i tried to work it out to solve for x using the equation you gave me..

Time (60 min) = 3/x + 5/(x+4)

then i used the LCD to get the x out of the denominator but i messed it up somehow...i'm just getting frustrated with a problem that should be easy as pi(no pun intended).

[John]

Imo it should be

1 = 3/x + 5/(x+4)

Not 60 =

Because we are dealing with Miles per hour not miles per minute

[ross]

Imo it should be

1 = 3/x + 5/(x+4)

Not 60 =

Because we are dealing with Miles per hour not miles per minute

my thoughts exactly but i tried the problem both ways anyway

[Kip Drordy]

Actually it would have been easier to use 1 hour instead of 60 min. (hint hint quadratic)

[ross]

so if i take the equation 1=3/x + 5/(x+4) and move 3/x to the other side, then cross multiply i get the answer of x=6...only problem i see now is that when i move 3/x to the other side, it should become -3/x and then the equation doesn't result in x=6

[Kip Drordy]

here we go:

1=3/x + 5/(x+4)

cross multiply 3/x and 5/(x+4) to then add fractions

you should end up with:

1 = (3x + 5x + 12) / x^2 + 4x

move the right side of the equation to the left and set to 0:

x^2 + 4x - 3x - 5x - 12 = 0

add like terms:

x^2 - 4x -12 = 0

Plug and chug in the quadratic equation and you'll get values of -2 and 6

Since you can't travel at a negative speed 6 is your answer.

[ross]

here we go:

1=3/x + 5/(x+4)

cross multiply 3/x and 5/(x+4) to then add fractions

you should end up with:

1 = (3x + 5x + 12) / x^2 + 4x

move the right side of the equation to the left and set to 0:

x^2 + 4x - 3x - 5x - 12 = 0

add like terms:

x^2 - 4x -12 = 0

Plug and chug in the quadratic equation and you'll get values of -2 and 6

Since you can't travel at a negative speed 6 is your answer.

sweet..thanks man i couldn't get it through my head how to set it up as a quadratic.

[BornSinner]

it's all good man

Let me know if you need any other help