sauer: Seven years ago, Julia's mum was twice as old as Julia. Today Julia's mum is 31. How old is Julia?

Julia is nineteen years old now

Lyzbet:
Julia is nineteen years old now

Explain ... Equations?

^^^

Julia =x

Mum= y


2x=y-7

Since julias mum is now 31 , we substitute

2x=31-7

2x=24

X=12

X + 7 years

oladayo042: If five people can kill five rats in five minutes, how many rats will fifty-five people kill in fifty-five minutes?

If these five people killed five rats in five mins then fifty five people will only kill fifty five rats in fifty five mins!

Now if EACH of these five people killed five rats in five mins (meaning they killed 25 rats in total) then fifty five people will kill 3025 rats in a fifty five mins period.

sauer: If you have three apples and you took away two, how many will you have?

ans 1apples

purplekayc: ^^^

Julia =x

Mum= y


2x=y-7

Since julias mum is now 31 , we substitute

2x=31-7

2x=24

X=12

X + 7 years

tot u didnt kw it. Good job, welldone

Dochido: ans 1apples

You will still have all three apples oo!

Question:
The marvel hero, Flash is to run against a tortoise. He gives the tortise a head start. So after tortoise gets to point A, Flash starts to run to catch up with the tortoise. But the claim is that Flash will never catch up with Mr. Tortoise. How then? Flash has to get to point A before we can say he's caught up with tortoise. But by then, Mr. Tortoise is in point B, i.e. point B - A ahead. Flash has to run that distance. When Flash gets to point B, Mr. Tortoise is now in point C. So, it goes and Flash never catches tortoise. Can someone logically explain whatz happening?

Q:

There was an Ijebu man who lived near a hill.

Every Monday morning @ 9am, he would walk a path from his home to the top of this hill, meditate and pray.

Then Tuesday morning @ 9am, he would walk the same path from the top of the hill back to his home.

Is there any time at which he crossed the same spot on both Monday and Tuesday?

^yes, mid way

What do you mean by midway?

ekt_bear: Q:

There was an Ijebu man who lived near a hill.

Every Monday morning @ 9am, he would walk a path from his home to the top of this hill, meditate and pray.

Then Tuesday morning @ 9am, he would walk the same path from the top of the hill back to his home.

Is there any time at which he crossed the same spot on both Monday and Tuesday?

Is this math? or quantitative reasoning?

ekt_bear:

My dear, if there exists a SPOT where they cross paths, then necessarily there exists a TIME, right?

So how can you say it is impossible to tell if there is such a time?

Like I keep saying, the speed he goes in either direction is irrelevant to the existence of a time.

Your question was interpreted to have asked if there was a particular time when the man or both men were at the same spot.
e.g 20m from his home at 11am on both Monday and Tuesday.

Hence my very first response:

Let's say the journey to the hill top takes a total of 2 hrs
Assuming he walks at the same speed all the way to and fro.

At 10am on Monday and Tuesday, he'd be halfway between the his home and the hill top.

What you now seem to be asking is whether they would have crossed paths at any time which is a different question.

some-girl:


Let's say the journey to the hill top takes a total of 2 hrs
Assuming he walks at the same speed all the way to and fro.

At 10am on Monday and Tuesday, he'd be halfway between the his home and the hill top.

OK. So what if:
a) His speed is not constant. Say he is accelerating at 1 meter/second^2 or something.
b) he doesn't walk at the same speed going up the hill as down the hill. So pretend he goes up the hill with velocity 1 m/s, but down the hill with velocity 2 m/s.

What then? Is it still true that there is some time at which he is at the same spot on both days?

You are on the right track though...push it further and see if you can generalize.

purplekayc:
Is this math? or quantitative reasoning?

When I solved the problem, I did so using math. But you can actually solve it using elementary reasoning too.

ekt_bear:

OK. So what if:
a) His speed is not constant. Say he is accelerating at 1 meter/second^2 or something.
b) he doesn't walk at the same speed going up the hill as down the hill. So pretend he goes up the hill with velocity 1 m/s, but down the hill with velocity 2 m/s.

What then? Is it still true that there is some time at which he is at the same spot on both days?

You are on the right track though...push it further and see if you can generalize.


When I solved the problem, I did so using math. But you can actually solve it using elementary reasoning too.

I wonder how you solved it with unknown variables on both sides of the equation.

Hmm. OK, so I'll give away the answer? Or rather give a hint that basically tells you the answer.

What happens if we merge the two days? Pretend that is an identical old man walking down the hill Monday at 9am?

sauer: Question: The marvel hero, Flash is to run against a tortoise. He gives the tortise a head start. So after tortoise gets to point A, Flash starts to run to catch up with the tortoise. But the claim is that Flash will never catch up with Mr. Tortoise. How then? Flash has to get to point A before we can say he's caught up with tortoise. But by then, Mr. Tortoise is in point B, i.e. point B - A ahead. Flash has to run that distance. When Flash gets to point B, Mr. Tortoise is now in point C. So, it goes and Flash never catches tortoise. Can someone logically explain whatz happening?

pointC marks the end of the contest.

Lord_Reed:

I wonder how you solved it with unknown variables on both sides of the equation.

Abeg tell am !

ekt_bear: Hmm. OK, so I'll give away the answer? Or rather give a hint that basically tells you the answer.

What happens if we merge the two days? Pretend that is an identical old man walking down the hill Monday at 9am?

Without a speed assumption how do you determine how much distance he covers?

Lord_Reed:

Without a speed assumption how do you determine how much distance he covers?

Well, think about it this way. Call our original Ijebu man Tunde. Now, whatever speed the man Tunde travels on Tuesday, pretend there is an identically fast old man (Femi) who is walking down the hill a day earlier (on Monday).

So, Tunde is walking up this hill Monday @ 9am, Femi is walking down the hill Monday @ 9am. They are on the exact same path. So of course, at some point, they will have to walk past each other. So there is some time at which they are both at the same position.


(Just FYI, this simple explanation is NOT the one i initially came up with when I solved this problem...I did something a lot more complicated and less elegant).

Kind of a neat brain teaser, no?

Off Topic post, apologies.

ekt_bear: ....

Bro, I just read that NYT link in your profile. Good read.

Have you read John Ogbu's work? He was a Berkeley Prof. of Sociology. His work "A Study of Academic Disengagement" was a seminal research on that topic. Died years ago. He was from Nigeria too.

He identified immigrant culture as the reason for the disparity explained in that article and not innate intelligence or anything like that.

I wonder how African immigrant kids (1st - 2nd Gen ) do on that New York test, I won't be surprised if they compare well with Asians.

Review here: http://www.hepg.org/her/abstract/38

Ogbu's bio: http://www.universityofcalifornia.edu/senate/inmemoriam/johnogbu.htm

ekt_bear:

Well, think about it this way. Call our original Ijebu man Tunde. Now, whatever speed the man Tunde travels on Tuesday, pretend there is an identically fast old man (Femi) who is walking down the hill a day earlier (on Monday).

So, Tunde is walking up this hill Monday @ 9am, Femi is walking down the hill Monday @ 9am. They are on the exact same path. So of course, at some point, they will have to walk past each other. So there is some time at which they are both at the same position.


(Just FYI, this simple explanation is NOT the one i initially came up with when I solved this problem...I did something a lot more complicated and less elegant).

Kind of a neat brain teaser, no?

Okay now we have a speed assumption so in this case we can say that since Femi is faster than Tunde they will meet somewhere off center towards Tunde's starting point.

It's not really a brain teaser as there are to many likely endings based on the parameters someone considering the setup would choose. A brain teaser should have very specific answers that require a tortuous route to the answer.

Lord_Reed:

Okay now we have a speed assumption so in this case we can say that since Femi is faster than Tunde they will meet somewhere off center towards Tunde's starting point.

It's not really a brain teaser as there are to many likely endings based on the parameters someone considering the setup would choose. A brain teaser should have very specific answers that require a tortuous route to the answer.

The point is that, the answer is INDEPENDENT of what the speed of the guy going up the hill Monday at 9am and his speed going down Tuesday 9am.

No matter what the speed functions are (or even more simply, position functions are), there is bound to be some time at which he crosses the same spot on both days.

That is why the puzzle is kind of cool.

Kilode?!:
Off Topic post, apologies.



Bro, I just read that NYT link in your profile. Good read.

Have you read John Ogbu's work? He was a Berkeley Prof. of Sociology. His work "A Study of Academic Disengagement" was a seminal research on that topic. Died years ago. He was from Nigeria too.

He identified immigrant culture as the reason for the disparity explained in that article and not innate intelligence or anything like that.

I wonder how African immigrant kids (1st - 2nd Gen ) do on that New York test, I won't be surprised if they compare well with Asians.

Review here: http://www.hepg.org/her/abstract/38

Ogbu's bio: http://www.universityofcalifornia.edu/senate/inmemoriam/johnogbu.htm

Hey, we should probably move this discussion to another thread

ekt_bear:

The point is that, the answer is INDEPENDENT of what the speed of the guy going up the hill Monday at 9am and his speed going down Tuesday 9am.

No matter what the speed functions are (or even more simply, position functions are), there is bound to be some time at which he crosses the same spot on both days.

That is why the puzzle is kind of cool.

It is dependent. Of course they would meet but the point is that with each speed variation the position will change. This is not a brain teaser challenge.

The question does not ask:

a) "what time does he visit the same spot", or
b) "what is this same spot visited."

It asks,
c) "is there a time he visits the same spot?"

The answer to (c) is independent of his velocity.

Anyway, no worries, if you didn't find it interesting, so be it.

yinka2392: pointC marks the end of the contest.

Not the right answer. When flash gets to point C, tortoise is already at point D since it's always in motion as well.

sauer: Question:
The marvel hero, Flash is to run against a tortoise. He gives the tortise a head start. So after tortoise gets to point A, Flash starts to run to catch up with the tortoise. But the claim is that Flash will never catch up with Mr. Tortoise. How then? Flash has to get to point A before we can say he's caught up with tortoise. But by then, Mr. Tortoise is in point B, i.e. point B - A ahead. Flash has to run that distance. When Flash gets to point B, Mr. Tortoise is now in point C. So, it goes and Flash never catches tortoise. Can someone logically explain whatz happening?

Flash is running as fast as the tortoise.

Lord_Reed:

Flash is running as fast as the tortoise.

Hmmm.... NOOO!

sauer:
Hmmm.... NOOO!

Ok Flash is running in reverse.

no. Flash is not running in reverse. They run in the same direction. Tortise just appears to be ahead, even though Flash is faster. There must be an explanation for this.

sauer: no. Flash is not running in reverse. They run in the same direction. Tortise just appears to be ahead, even though Flash is faster. There must be an explanation for this.

Its been almost a month since you put up your teaser, about time you gave the answer.