Playing with Math...

**vieome** · 15-Jul-13, 01:11 PM

Originally Posted by Dave S

And here's one that needs a little thought, also quite old, but a good test of one's observation based on the facts to hand.

An electric train leaves JHB at 60Kms/hour headed for Cape Town, at the same time a Diesel train leaves CapeTown at 40Km/hour headed for JHB, at the point where the train locomotives intersect, which train is furthest from JHB?

I also get the same distance. Intersect=meet cross lines. Where they meet on the track the distance from Joburg would be equal. Not sure if direction has anything to do with the answer.

**Dave S** · 15-Jul-13, 01:41 PM

Originally Posted by vieome

I also get the same distance. Intersect=meet cross lines. Where they meet on the track the distance from Joburg would be equal. Not sure if direction has anything to do with the answer.

Aaah yes, but the statement says "at the point where the locomotives intersect...". The point is not to assume anything, a locomotive pulls a series of carriages that are the train, the locos are not the train, they only pull it. At the point where the locos intersect, the train is still behind the respective loco, therefore, the JHB-CT train (by virtue of it's speed) has travelled further than the CT-JHB train, but it is still closer to JHB than the other train. The diesel train (CT-JHB) is thus still further from JHB.

The powers of observation are still relevant even in our imagination, and therefore, our interpretation of a question. I'm sure this is something that lawyers get used to, I. E. not assuming anything...

**vieome** · 15-Jul-13, 01:59 PM

Okay more like an English excercise lol.

I live on the 15th floor of a building.
Each day I catch the elevator to the 10th floor and walk take the stairs to the 15th. The elevator goes to the 15th. I am no doing it for health. Why the 10th.

**pmbguy** · 15-Jul-13, 02:21 PM

Dwellims

**Dave S** · 15-Jul-13, 02:28 PM

Originally Posted by vieome

Okay more like an English excercise lol.

I live on the 15th floor of a building.
Each day I catch the elevator to the 10th floor and walk take the stairs to the 15th. The elevator goes to the 15th. I am no doing it for health. Why the 10th.

A mix between English/Maths/logic...

There appears to be nothing in the statement that relates to a reason for you to take the stairs, but I haven't yet examined all the options/reasons... lol

1. The buttons 11 to 15 are busted
2. You have a fetish for stairs above 10th
3. Can only count to ten
4. Are too short to reach the higher buttons and/or left your high-heels on the bus
5. Your favourite views are out the stairwell windows from floors 10 through 15
6. Others... (to follow)

**pmbguy** · 15-Jul-13, 02:45 PM

You are married and you doing it for the health of your wife. The stairs exercise, therefore the 10th floor. You and or your wife deem 5flights of stairs sufficient for now.

edit "I am no doing it for health"
Because the writer only seems to be referring to him/her self, I may refer to another person when I say it’s for the wife’s health)

**vieome** · 15-Jul-13, 02:57 PM

Originally Posted by Dave S

4. Are too short to reach the higher buttons and/or left your high-heels on the bus

Close enough , I am a migit, or PC(small person)

**Dave S** · 15-Jul-13, 03:03 PM

Originally Posted by vieome

Close enough , I am a migit, or PC(small person)

YeeeeeeHaaaaa!

**tec0** · 15-Jul-13, 11:16 PM

It is seemingly obvious that Velocity = Displacement/Time and that Speed = Distance/Time yet there is a condition where Velocity = Speed... The exception that proofs the rule? Maybe... [It is easy you don't have to google it

]

**Dave S** · 16-Jul-13, 07:13 AM

Only if an object is travelling at a constant speed, in a straight line, in a constant direction, without effect of acceleration/deceleration, between points "a" and "b", can it be said that the object velocity = the object speed. In such a case displacement would be equal and we now only require to calculate the distance/time.

Picture in your minds eye, a bullet fired from a gun, when the bullet leaves the muzzle of the gun, this is the last point where the velocity and speed of the bullet are equal. As the bullet loses momentum so it begins to fall to earth, thereby changing it's direction and its displacement, eventually the bullet will stop at some point. A straight line to that point [where the bullet landed] is the displacement (or the distance the bullet has moved away from the gun), divide this by the time it took for the bullet to get there, equals the VELOCITY of the bullet. Now imagine the full arc that the bullet has travelled, (or the distance the bullet has travelled), divide this by the time it took for the bullet to get there equals the SPEED of the bullet.