Comments on: Episode 54: Math Anxiety – Causes and Cures

By: David W.

David W. — Mon, 07 Nov 2011 22:29:05 +0000

He profited $20.

If he starts with $50, then after buying the horse for $20, he has $30. After selling it for $30, he has $60. When he buys it back for $40, he has $20. After selling it again for $50, he has $70. He started with $50 and ended with $70. He profited $20.

I’m not sure how anyone thinks he broke even. It really does not matter if its the same horse each time or not.

By: Anne McLoughlin

Anne McLoughlin — Sun, 21 Aug 2011 12:37:54 +0000

He started off with $30 in his wallet.
He paid out $20.Then got back $30 from selling horse.
$30+$10=$40
Now he spends entire $40 to buy back horse and sell it for $50.
Now he has $50 in his wallet. So profit of $20

By: Maura

Maura — Sun, 31 Jul 2011 16:21:10 +0000

I think that the man made a profit of £20. If he began with £100 in his pocket spent it on the horse he is left with £80.Then he sells it for £30 so he now has £110 . Next he buys it back for £40.So now he has £70. Finally he sells it for £50 so he ends up with £120 which means he has made a profit of £20.

By: Nicholas Corwin

Nicholas Corwin — Sat, 30 Jul 2011 18:20:17 +0000

One further note: when I said it is partially correct to assert that the buyer earned a $20 total profit, I meant the following: If you look at each transaction separately, you could say that he earned a $10 profit twice, for a total of $20, but that reasoning ignores the money he laid out. In any case, here, such is not the case, because it’s the same horse. This fact, I would argue, is significant: the problem states that he “buys the horse back.” If it were two entirely separate transactions, you could argue that he made a $20 “profit” in the aggregate.

By: Nicholas Corwin

Nicholas Corwin — Sat, 30 Jul 2011 18:11:24 +0000

Well, now, it seems we’re straying from a purely mathematical problem into a kind of philosophical or semantic one. You can’t say “it doesn’t matter if it is the same horse or not,” because the facts of the problem state explicitly that he “buys the horse back.” Hence, with all due respect, Jim, supra, is at best only partially correct to assert that the buyer earned a $20 profit.

The first sale generated a profit of $10, it is true, and the second one appears to have generated a profit of $10. However, the second time around, the seller laid out $40 for the same item, erasing his previous $10 profit and costing him an additional $10. So at this point he has a loss (or money laid out) of $10. Then he sells it for $50, recouping his $10 loss, but earning no additional money. In short, he breaks even.

By: Jim

Jim — Thu, 01 Apr 2010 16:37:31 +0000

Regarding the selling of the horse, I would look at each instance of buying and selling instead of adding them up to get zero.
In the first instance, he bought a horse for $20 and sold it for $30, a profit of $10.
He then bought it (it doesn’t matter if it is the same horse or not) for $40 and sold it for $50, a profit of $10. In total, he made a profit of $20.
In a spread sheet, he would have a total of $60 going out, and a total of $80 coming in, for a profit of $20.
If you look at his net worth (say $100 to start with) it would go down to $80, up to $110, down to $70, and then up to $120. Again, a profit of $20.

By: Michael

Michael — Wed, 03 Jun 2009 22:20:21 +0000

Andy: I’ll send your solution to Dr. Geist to see if you’re right! Michael

By: Andy

Andy — Tue, 02 Jun 2009 21:44:31 +0000

I think I know the answer to the question above about the horse. looking at the problems the man buy a horse for 20, then sell it to for 30 and buys it back for 40 and sells it again for 50. the person lost 20 for buying the horse, but he again 10 for selling it. Then he lost the 10 for buying it back and another ten for selling the horse.
So: -20 + 10 = -10,
-10 – 40 = -50
-50 + 50 = 0
The person break even>