Author Topic: How fast can Ron cycle? (Read 7594 times)

Ergot · « **on:** May 16, 2006, 01:50:16 am »

In one hour Dan drives 25 miles farther in his car than Ron can cycle on his bike. If it takes Ron one and a half hours longer to cycle 75 miles than it takes Dan in his car, how fast can Ron cycle?

Sidoh · « **Reply #1 on:** May 16, 2006, 02:13:44 am »

Not sure if this is right. I'm pretty sick and it's late.

R = D - 25
D = 1.5R
25 = 1.5R - R
25 = R(1.5 -1)
R = 25/.5
R = 50

Ergot · « **Reply #2 on:** May 16, 2006, 02:56:45 am »

Doesn't 50 mph on a bike seem a little umm... far fetched?

Sidoh · « **Reply #3 on:** May 16, 2006, 03:09:45 am »

Quote from: Ergot on May 16, 2006, 02:56:45 am

Doesn't 50 mph on a bike seem a little umm... far fetched?

On average, yeah, but it's definitely possible. I'm pretty sure I've done it before (downhill, but still).

I see my problem, though... hold on. Working on a intelligible answer.

Ergot · « **Reply #4 on:** May 16, 2006, 03:38:25 am »

Well I started with rt=D
So r_D*t = (r_R*t) + 25
t = 1 so I get r_D = r_R + 25

75 = r_R(t_D + 3/2)

r_D*t_D = 75
Subsititute this up there...

75 = r_R(75/r_D + 3/2)
Then we plug in r_D that we found in the beginning...
75 = r_R(75/(r_R + 25) + 3/2)
Solving... 0 = 3r_R² + 225r_R - 75

I'm not doing something right... so I tried r=t/d but then that just got me something stupid too x_x

Nate · « **Reply #5 on:** May 16, 2006, 07:50:10 pm »

False or 16 2/3 MPH

Ergot · « **Reply #6 on:** May 16, 2006, 09:27:33 pm »

Quote from: Nate on May 16, 2006, 07:50:10 pm

False or 16 2/3 MPH

How'd you get it?

Nate · « **Reply #7 on:** May 16, 2006, 09:47:49 pm »

t = time, D = Dan's rate, R = Ron's rate
EQ 1. tD-tR=25 when t =1
EQ 2. tD = (t+1.5)R
sub EQ 2 in EQ 1
1.5R = 25
R = 50/3

Ergot · « **Reply #8 on:** May 16, 2006, 10:07:12 pm »

According to my calculations... (they might be wrong...)
It'll take Ron 4.5 hours for 75 miles.
It'll take Dan 1.8 hours for 75 miles.
4.5 - 1.8 != 1.5 ? I'm not saying you're wrong... but the difference in their time doesn't work out for me... can you show me Dan's rate/time too ?

Nate · « **Reply #9 on:** May 16, 2006, 10:35:40 pm »

I get 37.5 MPH for Dan.

Ergot · « **Reply #10 on:** May 16, 2006, 10:57:22 pm »

Quote from: Nate on May 16, 2006, 10:35:40 pm

I get 37.5 MPH for Dan.

Then 4.5 hours for Ron... 2 hours for Dan. That's still not a 1.5 hour difference

?

Joe · « **Reply #11 on:** May 17, 2006, 08:13:54 am »

Does this have anything to do with iago and Quik?

iago · « **Reply #12 on:** May 17, 2006, 01:42:57 pm »

Quote from: Sidoh on May 16, 2006, 03:09:45 am

Quote from: Ergot on May 16, 2006, 02:56:45 am
Doesn't 50 mph on a bike seem a little umm... far fetched?

On average, yeah, but it's definitely possible. I'm pretty sure I've done it before (downhill, but still).

I see my problem, though... hold on. Working on a intelligible answer.

Doubt it. My absolute highest speed (downhill, wind behind me, pedalling as hard as I could) was 58km/h, or 36mph.

Sidoh · « **Reply #13 on:** May 17, 2006, 01:53:17 pm »

Quote from: iago on May 17, 2006, 01:42:57 pm

Doubt it. My absolute highest speed (downhill, wind behind me, pedalling as hard as I could) was 58km/h, or 36mph.

Yeah, but you have a Canadian bike. Canadian bikes don't have nuclear fuel cells. Duh.

BigAznDaddy · « **Reply #14 on:** May 17, 2006, 05:05:05 pm »

Quote from: Ergot on May 16, 2006, 03:38:25 am

Well I started with rt=D
So r_D*t = (r_R*t) + 25
t = 1 so I get r_D = r_R + 25

75 = r_R(t_D + 3/2)

r_D*t_D = 75
Subsititute this up there...

75 = r_R(75/r_D + 3/2)
Then we plug in r_D that we found in the beginning...
75 = r_R(75/(r_R + 25) + 3/2)
Solving... 0 = 3r_R² + 225r_R - 75

I'm not doing something right... so I tried r=t/d but then that just got me something stupid too x_x

what is all this gibberish

Nate · « **Reply #15 on:** May 17, 2006, 09:38:16 pm »

Then i go with my original answer of False. Their speeds aren't constant.

iago · « **Reply #16 on:** May 17, 2006, 10:30:46 pm »

Quote from: BigAznDaddy on May 17, 2006, 05:05:05 pm

Quote from: Ergot on May 16, 2006, 03:38:25 am
Well I started with rt=D
So r_D*t = (r_R*t) + 25
t = 1 so I get r_D = r_R + 25

75 = r_R(t_D + 3/2)

r_D*t_D = 75
Subsititute this up there...

75 = r_R(75/r_D + 3/2)
Then we plug in r_D that we found in the beginning...
75 = r_R(75/(r_R + 25) + 3/2)
Solving... 0 = 3r_R² + 225r_R - 75

I'm not doing something right... so I tried r=t/d but then that just got me something stupid too x_x

what is all this gibberish

It's called math. You're making a pretty lousy first impression here -- reminds me of the classic quote, "It's better foor one to be silent and thought a fool than to open one's mouth and remove all doubt"

dark_drake · « **Reply #17 on:** May 18, 2006, 02:37:26 am »

Ron is going 25mph?
Edit: If only this were in the homework board, I would've seen it earlier.

Ergot · « **Reply #18 on:** May 18, 2006, 03:20:48 am »

Yea, how'd you get it? (I still didn't get it

).

TeHFoOoL · « **Reply #19 on:** June 16, 2006, 02:25:36 am »

Quote from: iago on May 17, 2006, 10:30:46 pm

Quote from: BigAznDaddy on May 17, 2006, 05:05:05 pm
Quote from: Ergot on May 16, 2006, 03:38:25 am
Well I started with rt=D
So r_D*t = (r_R*t) + 25
t = 1 so I get r_D = r_R + 25

75 = r_R(t_D + 3/2)

r_D*t_D = 75
Subsititute this up there...

75 = r_R(75/r_D + 3/2)
Then we plug in r_D that we found in the beginning...
75 = r_R(75/(r_R + 25) + 3/2)
Solving... 0 = 3r_R² + 225r_R - 75

I'm not doing something right... so I tried r=t/d but then that just got me something stupid too x_x

what is all this gibberish

It's called math. You're making a pretty lousy first impression here -- reminds me of the classic quote, "It's better foor one to be silent and thought a fool than to open one's mouth and remove all doubt"

This is probably my third or fourth post crushing him. /signed.

Here's a few tips since this is probably your first forum ever:

1. Don't post about stuff you don't know.
2. Don't post something like; "yeah", "no", or " no that's not right ( without an explanation why. )
3. Don't post stuff like " what is all this gibberish? "

News:

Author Topic: How fast can Ron cycle? (Read 7594 times)