Monday, August 27, 2007

Problem 1 - Fake Note problem

Hey guys,

It has been a long time since I wrote on the blog. I had said that I would come up with a website to help people preparing for CAT after I got a good response for the GD and PI preparation. But, since I had to travel overseas on some assignment for three months I could not devote enough time to get the website on. So I thought that atleast I should devote some time for your CAT prep. So I will be putting some very very simple but interesting problems on the blog that people can come and answer. I promise enough traps in each problem that will help you hone your basics.

Most problems will be on probability, which people find hard to master and I think I am fairly good at. But let me start with a simple arithmetic problem. It will be on for a week and people can post their answers with reasons on the comment section.
Rope in as many guys as you know. More guys, more perspectives and better learning.

So here goes the first problem.

Dell goes to a store to buy a new cheap ipod that has come in the market. He gives $5 to Lenovo who is the shop owner.
The ipod is worth $3, but Lenovo does not have change. He goes to Acer who owns a “pc world” next door and gives him $5 to get back five $1 bills in return.
He comes back and returns $2 to Dell and gives him his ipod.
After a while Acer comes and says that the $5 bill that lenovo gave was a fake one. Lenovo is disappointed that he got cheated, but gives Acer a new $5 and tears the fake bill.
How much does Lenovo lose?

The choices are a) 5 b) 7 c) 10 d) 3 e)None of these

Please give reasons for your answers. And dont read the other comments only after you have put in you answer.

Click Here for answer


Anonymous palzor said...

10 as he looses ipod+$2 and $5 to acer

6:11 AM, August 27, 2007  
Anonymous Anonymous said...

To start with he had an Ipod. Now he has lost that and $5 to Acer.. looks like he is in a loss of $8... I am always a little skeptical of choosing 'none of these' as an answer though :)

6:16 AM, August 27, 2007  
Blogger Gyan-ee said...

Got a mail saying that some people at Pagalguy got it right. I dont mind people posting the questions on pagalguy, since it would benifit more people. But if you guys can also put the answers here, it would benifit all and also help me answer queries

Yes the answer is $5. Here are some fundas on how to think simple and not get confused.

1. Lenovo's loss has to be somebody's gain. Dell gained $5 (he started with a fake note ehich was equivalent to 0) and Acer gained/lost nothing.

2. If the note was not fake, no one would have lost anything. The note being fake is equivalent to Acer misplacing the $5.

3. The only thing that got destroyed is the $5 note and hence that is the loss.

Hope it clears things. This problem was just to demonstrate how we make silly mistakes in simple everyday problems. I am sure if you were Acer yourself (a small kirana shop owner), you would have realised your loss amount easier :)

11:18 PM, August 28, 2007  
Blogger tanu said...

c but u r askin lenovos loss w/c is d loss he incurs due 2 sale of ipod + $2change w/c he gave + 5$ w/c he gave it 2 acer ...w/c a/cs to 10$.....

12:27 AM, September 01, 2007  
Blogger Gyan-ee said...


He gave Acer back what he had got from him earlier. So there is no loss on that. (If he had lost, then Acer should have gained which he has not)

He sold and ipod and gave 2$ to dell for nothing in return. That is his loss.

Hope I am clear

2:09 AM, September 03, 2007  
Anonymous nee said...

Thanks Gyan-ee, this was an interesting problem. After readign your solution I came up with another way of looking at it. Suppose Lenovo started with an ipod worth 3$ and 5$, so his net worth is 8$. he exchanged 5$ with 5 1$ and gave 2$ and ipod to dell. so he has no ipod but 5+3=8$. After he retuens 5$ to acer, he has only 3$ left, so the loss is, 8-3=5$.

Have I simplifies things or made them more complicated??!!??

4:09 AM, September 03, 2007  
Blogger Nirvana !!? said...

cause what he lost was 1) ipod (ie $3)
2) the change he returned($2)

11:59 AM, September 12, 2007  
Blogger Gyan-ee said...

You are right Nirvana

11:58 PM, September 12, 2007  

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