C4 Math Problem
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C4 Math Problem
This was in the newspaper this morning and a little bit of an *** kicker. The problem is easy to solve after you think about it but the obvious answer that you want to say at first is incorrect.
If your ricer is traveling 60 MPH it takes 1 minute to travel 1 mile.
If your Corvette is traveling 120 MPH it takes 30 seconds to travel 1 mile.
How fast must your Lincoln be going to travel the mile in exactly 45 seconds?
If your ricer is traveling 60 MPH it takes 1 minute to travel 1 mile.
If your Corvette is traveling 120 MPH it takes 30 seconds to travel 1 mile.
How fast must your Lincoln be going to travel the mile in exactly 45 seconds?
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Originally Posted by Nathan Plemons
This was in the newspaper this morning and a little bit of an *** kicker. The problem is easy to solve after you think about it but the obvious answer that you want to say at first is incorrect.
If your ricer is traveling 60 MPH it takes 1 minute to travel 1 mile.
If your Corvette is traveling 120 MPH it takes 30 seconds to travel 1 mile.
How fast must your Lincoln be going to travel the mile in exactly 45 seconds?
If your ricer is traveling 60 MPH it takes 1 minute to travel 1 mile.
If your Corvette is traveling 120 MPH it takes 30 seconds to travel 1 mile.
How fast must your Lincoln be going to travel the mile in exactly 45 seconds?
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From: Punta Gorda, FL
St. Jude Donor '03-'04-'05-'06-'07-'08-'09-'10-'13- '14
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I was thinking it would be 90. So why is it 80?
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From: Dunstable MA
St. Jude Donor '05
Extra credit: if you use the highways a lot; do the math about how much time is saved by traveling 85 cuz you're in a hurry, over going 75 and staying with the traffic. It has to be a long ride to matter much. Now, getting to 105 going through the gears to get on the highway, that's controlled by something else.
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From: Austin Texas
Originally Posted by vetteweiser
I was thinking it would be 90. So why is it 80?
yeah...me too...but at 90mph :90mile/3600sec = X mile/45sec cross multiply ==> X = 1.125 Mile
80mile/3600sec = X mile/45sec cross multiply ==> X = 1.00 Mile
I still think it is 90Mph damn it!!! I hated the SAT's and always will !!
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Originally Posted by vetteweiser
I was thinking it would be 90. So why is it 80?
60 MPH / 60 Seconds vs 120 MPH / 30 Seconds
Well you think that 45 seconds is half way between 30 and 60, 90 mph is half way between 60 and 120, must be right huh?
Unfortunately that's not the case.
To go from 60 to 120 you double it. To go from 60 to 30 you take half of it. Hmm, see the pattern? Anything you do to the top you have to take the INVERSE of on the bottom and vice versa. So 45 seconds is 3/4 of 60 seconds. This means you have to multipy the top by 4/3. 60*(4/3) = 80
Annyoying huh? My dad and I both said 90 first too. He's a math major from way back. He figured it out in another way, which basically accomplishes the same thing.
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From: Punta Gorda, FL
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Ok, that math is making my head hurt. Time to numb the brain up a little bit
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
The math is simple algebra:
To find the speed difference keep the distance the same and vary the time:
60 seconds over 1 mile 60/1 =
45 seconds over one mile 1 =
Cancel out the 1s you have 60/45 or 1.3333333 that's 60 seconds over 45 seconds going the same distance
That's the ratio of time over distance=speed. You're going 1.33 times FASTER. Distance is constant, and this gives you the INCREASED ratio you would need to cover the same distance in less time. Hence, the 1.33 ratio in speed.
Knowing that 60 miles an hour is one mile per minute, therefore 60x the new ratio, or 1.33333 is 80 miles per hour. You have to go 1.33 times faster to do a mile in 45 seconds.
However, since it was posted as a trick questions, and the right answer was already given, I took the time to figure it out.
My initial thought WAS 90 MPH before thinking it through.
To find the speed difference keep the distance the same and vary the time:
60 seconds over 1 mile 60/1 =
45 seconds over one mile 1 =
Cancel out the 1s you have 60/45 or 1.3333333 that's 60 seconds over 45 seconds going the same distance
That's the ratio of time over distance=speed. You're going 1.33 times FASTER. Distance is constant, and this gives you the INCREASED ratio you would need to cover the same distance in less time. Hence, the 1.33 ratio in speed.
Knowing that 60 miles an hour is one mile per minute, therefore 60x the new ratio, or 1.33333 is 80 miles per hour. You have to go 1.33 times faster to do a mile in 45 seconds.
However, since it was posted as a trick questions, and the right answer was already given, I took the time to figure it out.
My initial thought WAS 90 MPH before thinking it through.
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From: Columbia Missouri
Here's another one
Originally Posted by Nathan Plemons
Ok, here's the logic, set it up as a fraction.
60 MPH / 60 Seconds vs 120 MPH / 30 Seconds
Well you think that 45 seconds is half way between 30 and 60, 90 mph is half way between 60 and 120, must be right huh?
Unfortunately that's not the case.
To go from 60 to 120 you double it. To go from 60 to 30 you take half of it. Hmm, see the pattern? Anything you do to the top you have to take the INVERSE of on the bottom and vice versa. So 45 seconds is 3/4 of 60 seconds. This means you have to multipy the top by 4/3. 60*(4/3) = 80
Annyoying huh? My dad and I both said 90 first too. He's a math major from way back. He figured it out in another way, which basically accomplishes the same thing.
60 MPH / 60 Seconds vs 120 MPH / 30 Seconds
Well you think that 45 seconds is half way between 30 and 60, 90 mph is half way between 60 and 120, must be right huh?
Unfortunately that's not the case.
To go from 60 to 120 you double it. To go from 60 to 30 you take half of it. Hmm, see the pattern? Anything you do to the top you have to take the INVERSE of on the bottom and vice versa. So 45 seconds is 3/4 of 60 seconds. This means you have to multipy the top by 4/3. 60*(4/3) = 80
Annyoying huh? My dad and I both said 90 first too. He's a math major from way back. He figured it out in another way, which basically accomplishes the same thing.
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Originally Posted by VFR750
A driver runs 30 MPH for his first lap (in his MG I guess). How fast does he have to go for the second lap to bring his average up to 60 MPH for the two laps? :o
There are two laps, you want the average to be 60. Multiply the average by the number of laps and you get 120. 120-30 = 90
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From: Columbia Missouri
Originally Posted by Nathan Plemons
Well my first instinct would be 90, the logic being the following.
There are two laps, you want the average to be 60. Multiply the average by the number of laps and you get 120. 120-30 = 90
There are two laps, you want the average to be 60. Multiply the average by the number of laps and you get 120. 120-30 = 90
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From: SE NY
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When I travel the now boring drive between SE NY and NE OH I often do the mental math on how much time I can shave off the 450 mile trip by traveling at different speeds. I start with the premise that I can make the trip in 7 1/2 hrs at 60mph and go from there with the mental math of doint 5, 10, 15, etc over the posted vs savings in travel time.
And still I fell into the trap on this one. Now I'll have to check all that "mental math" for validity.
And still I fell into the trap on this one. Now I'll have to check all that "mental math" for validity.
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From: Texas
Originally Posted by Bilyk
wtf?
the lincoln is doing 1mile/45 sec
which is 1.333333... miles / minute
which is 80 miles / hour
why would it be 90?!?!
the lincoln is doing 1mile/45 sec
which is 1.333333... miles / minute
which is 80 miles / hour
why would it be 90?!?!
alot of you guys are trying way too hard on this one...
there are 3600 seconds on an hour (60*60) all you need to do is divide 3600 by the amount of seconds you want to do the mile in and you get how many miles you will do in one hour or MPH
3600/45 seconds=80 MPH
3600/60 seconds=60 MPH
3600/30 seconds=120 MPH
3600/40 seconds=90 MPH
Last edited by OrthoAggie; Jan 16, 2005 at 04:02 PM.