View Full Version : The Math Game

spikejones

29-12-09, 23:39

Well.. its not a total game thread considering it takes some mental processing to figure this stuff out (hopefully its challenging enough). I'll start with something relatively easy and just as last time with the brain teasers thread -> he who gets it correct can post the next question. Lets keep this one math related although not too terribly hard so that we don't all feel like dummies :p

Right then...

You are getting ready for a trip that would normally have a duration of 1 hour, traveling at a constant rate of speed. However, you get held up by some traveling salesmen as you were just about to leave - causing you to leave 15 minutes later than you had originally planned. How much faster would you need to travel in order to arrive at the time you had originally planned? (either in fractional or percentage form)

I believe that would be 133 1/3 %. If it's wrong, I'm sorry I should be in bed 2 hours ago. :vlol:

spikejones

29-12-09, 23:53

HOLY CRAP BATMAN!!

that is really really fast.

and wrong.

I think you're on the right track though, but need some revising to your work.

HOLY CRAP BATMAN!!

that is really really fast.

and wrong.

I think you're on the right track though, but need some revising to your work.

Erm:

Given: s, t = 1h, t’ = 0.75*t, v

To find: v’

v = s/t <=> s = v*t

v’ = s’/t’ <=> s’ = v’*t’

s’ = s: v’*t’ = v*t

<=> v’*0.75*t = v*t

<=> v’*0.75 = v

<=> v’ = v/0.75 = 4/3 * v

So what Love2Raid said seems correct to me.

Why?

Say the distance is 10 km and you have a traveling speed of 10 km/hour, this will make you arrive one hour later, right on time.

Now, if you are delayed for 15 min by some dude, you have 0.75 hours left to make it in time. The speed will then be 10/0.75 is 13 1/3.

If 10 km/hour is 100% speed, 13 1/3 km/hour is (13 1/3 x 100):10 = 133 1/3%

spikejones

30-12-09, 00:33

Erm:

Given: s, t = 1h, t’ = 0.75*t, v

To find: v’

v = s/t <=> s = v*t

v’ = s’/t’ <=> s’ = v’*t’

s’ = s: v’*t’ = v*t

<=> v’*0.75*t = v*t

<=> v’*0.75 = v

<=> v’ = v/0.75 = 4/3 * v

So what Love2Raid said seems correct to me.

well I'll admit I'm lost by that equation there :vlol:

however, look to your last line:

v’ = v/0.75 = 4/3 * v

what I'm reading here from the first and last parts of the equality are that "new velocity equals 4/3 old velocity"

which is correct, however it does not translate out to 133 1/3 percent faster. The way I originally figured this out was on another forum where we were having a discussion of attack rate buffs, and I noticed a correlation to if you were to decrease your attack interval by 25%, it would increase your attack rate by 33.33~% (1/3).

Lets look at miles/hour and hours/mile as inverses of each other. That is:

1 / MPH = HPM (or MPH/(MPH^2) = HPM)

1 / HPM = MPH (or HPM/(HPM^2) = MPH)

therefore with a speed of 100 MPH:

1/100 = .01 hours per mile

//decrease time by 25%

.75 * .01 = 0.0075 hours per mile

1/.0075 = 133.33~ MPH

133.33~ - 100 = 33.33~

33.33~ / 100 = .33~ (ie 1/3 faster)

so with an unknown speed:

1/x hours per mile * .75 = .75/x hours per mile

(.75/x) / ((.75/x)*(.75/x)) = Y

(.75/x) / .5625/x^2 = Y

.75x^2 / .5625x = Y

1.333333333*x~ = Y

therefore, with Y being 133.33% of X, and X being itself 100%, the increase in speed is 33.33%.

Cochrane has gotten the most correct IMO before I started this reply. therefore he can go now.

miss.haggard

30-12-09, 00:53

This thread makes me feel dumb.

Necromanser

30-12-09, 01:03

You have any more problems?

This thread makes me feel dumb.

Nah, it really was a simple problem. Ignore all the math, it wasn't really necessary. You only need basic algebra.

You really have to READ the problem, and pay attention to what you read. You may think the wording (how much faster, rather than how fast) is a nit-pick. But ignoring details like this has caused NASA to lose several probes.

Classic, like the rumor game.

larasbestm8

30-12-09, 02:00

however, look to your last line:

v’ = v/0.75 = 4/3 * v

what I'm reading here from the first and last parts of the equality are that "new velocity equals 4/3 old velocity"

which is correct, however it does not translate out to 133 1/3 percent faster. The way I originally figured this out was on another forum where we were having a discussion of attack rate buffs, and I noticed a correlation to if you were to decrease your attack interval by 25%, it would increase your attack rate by 33.33~% (1/3).

Lets look at miles/hour and hours/mile as inverses of each other. That is:

1 / MPH = HPM (or MPH/(MPH^2) = HPM)

1 / HPM = MPH (or HPM/(HPM^2) = MPH)

therefore with a speed of 100 MPH:

1/100 = .01 hours per mile

//decrease time by 25%

.75 * .01 = 0.0075 hours per mile

1/.0075 = 133.33~ MPH

133.33~ - 100 = 33.33~

33.33~ / 100 = .33~ (ie 1/3 faster)

so with an unknown speed:

1/x hours per mile * .75 = .75/x hours per mile

(.75/x) / ((.75/x)*(.75/x)) = Y

(.75/x) / .5625/x^2 = Y

.75x^2 / .5625x = Y

1.333333333*x~ = Y

therefore, with Y being 133.33% of X, and X being itself 100%, the increase in speed is 33.33%.

o.0 *dies*

miss.haggard

30-12-09, 02:05

Nah, it really was a simple problem. Ignore all the math, it wasn't really necessary. You only need basic algebra.

You really have to READ the problem, and pay attention to what you read. You may think the wording (how much faster, rather than how fast) is a nit-pick. But ignoring details like this has caused NASA to lose several probes.

Classic, like the rumor game.

Yeah... about that. :ton:

Necromanser

30-12-09, 02:13

Since no-one's posting a problem, here's one:

If 32 men can renovate 6 flats in 24 days,how many extra men need to be employed to complete the job in 16 days?

32 men required to complete the job in 24 days.

=> 1 day requires 32men/24

16 days require (32men/24)*16 = 21.333 men

No extra men required.

Necromanser

30-12-09, 04:53

You can have 1/3 of a man, and also since you need to complete the same ammount of work in a smaller number of days you need more men.

How did you get 1/3 of a man? :confused:

Necromanser

30-12-09, 05:47

You said it's 21.33333 thats 21 and 1/3, thats the 1/3 I was referring to.You're on the right track though

:}hello friend

30-12-09, 05:49

Probably from your answer 21 1/3. You can have an 1/3 of a man working. That man would come to work and work a third of the time every other person does, If I am correct.

Poop.... -_-

I was beaten...

Necromanser

30-12-09, 05:52

Probably from your answer 21 1/3. You can have an 1/3 of a man working. That man would come to work and work a third of the time every other person does, If I am correct.

Poop.... -_-

I was beaten...

It's unlogical though, you can't get more work done in the same ammount of time with the same or less number of men.

@Necro: Oh okay :D

You would need 48 men.

How did you get that figure?

Necromanser

30-12-09, 06:34

32*(24/16)=48

So we do need more men? :o

Necromanser

30-12-09, 06:41

Yes we do, 16 more.

Yes we do, 16 more.

*hides in a corner*

I've been rusty >.<

CerebralAssassin

30-12-09, 10:31

awesome...a sequel to the brain teaser thread!!:p

what I'm reading here from the first and last parts of the equality are that "new velocity equals 4/3 old velocity"

which is correct, however it does not translate out to 133 1/3 percent faster.

Yes, that's what I meant, and yeah, I see the problem with Love2Raid's solution. But isn't that just semantics? :D

You would need 48 men.

That's what I got too: 6 flats require 32*24 = 768 mandays; to achieve 768 mandays in 16 days, you need 768/16 = 48 men.

And yes, requiring the answer to be "+33.3% instead of "=133.3%" is just semantics. :p

Yes, that's what I meant, and yeah, I see the problem with Love2Raid's solution. But isn't that just semantics? :D

Yes it is. :p

But according to aktrekker it could have serious consequences:

Nah, it really was a simple problem. Ignore all the math, it wasn't really necessary. You only need basic algebra.

You really have to READ the problem, and pay attention to what you read. You may think the wording (how much faster, rather than how fast) is a nit-pick. But ignoring details like this has caused NASA to lose several probes.

Classic, like the rumor game.

:eek:

I had better read those questions more carefully...>_>

Anyway, so here is my complete answer:

Say the distance is 10 km and you have a traveling speed of 10 km/hour, this will make you arrive one hour later, right on time.

Now, if you are delayed for 15 min by some dude, you have 0.75 hours left to make it in time. The speed will then be 10/0.75 is 13 1/3.

If 10 km/hour is 100% speed, 13 1/3 km/hour is (13 1/3 x 100):10 = 133 1/3%. So you need to go 133 1/3 - 100 = 33 1/3% faster. :cln:

It's unlogical though, you can't get more work done in the same ammount of time with the same or less number of men.

Well, you're going to need a whip if you want to get that done. http://www.ben-newman.de/smilie/misc/209070.gif

TombOfRaiders

30-12-09, 14:34

There's already a thread about this: http://www.tombraiderforums.com/showthread.php?t=160845&highlight=mathematics+game

Can a mod close this?

lara c. fan

30-12-09, 15:32

There's already a thread about this: http://www.tombraiderforums.com/showthread.php?t=160845&highlight=mathematics+game

Can a mod close this?

Glancing through it, I can't see the questions in this one.

They just seem to be simple ones....

spikejones

30-12-09, 22:08

There's already a thread about this: http://www.tombraiderforums.com/showthread.php?t=160845&highlight=mathematics+game

Can a mod close this?

boo!!:cen::spm:

Its over a month old though, likely buried where I didn't bother to look. I can see why you're hating though :mis: don't feel bad though, I made a brain teaser thread a while back that ran its course and died out - as all threads do (except the Britney thread that just wont die). I'm certainly not upset in the least bit that there's a new brain teaser thread in town.;)

sorry, my brain is on vacation right now - haven't come up with anything new yet. I'll check back later though to see whats new.:D

LaraLuvrrr

30-12-09, 22:25

I have 10 apples and I take away 7

How many do I have?

lara c. fan

30-12-09, 22:36

I have 10 apples and I take away 7

How many do I have?

7

Not getting past me :ohn:

Nah, I joke :p

You have ten becuase you took appples away from urself, then gave them back to yourself. Right :whi:

LaraLuvrrr

30-12-09, 22:45

7

Not getting past me :ohn:

lol! :p

Minty Mouth

30-12-09, 22:46

7

Not getting past me :ohn:

This is a joke right? :p

EDIT: Oh I get it! Clever :pi:

Ward Dragon

31-12-09, 05:45

Couldn't resist :p

http://imgs.xkcd.com/comics/newton_and_leibniz.png

CerebralAssassin

02-02-10, 04:47

seeing as this thread has drifted into the depths of hell...I'll revive it!:p

here's an interesting one I found: (even though some calculus is required,sorry:o )

One morning is starts to snow at a constant rate. Later, at 6:00am, a snow plow sets out to clear a straight street. The plow can remove a fixed volume of snow per unit time, in other words its speed it inversely proportional to the depth of the snow. If the plow covered twice as much distance in the first hour as the second hour, what time did it start snowing?

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