Brain Teaser

dadx2mj · Post by **dadx2mj** » Tue Sep 17, 2002 11:28 am

Here is a little brain teaser for all you brain -e-acks. I have never been able to solve this one so maybe someone here can.

Three guys order some pizza. When the delivery guy gets there he tell them it is $30 so they all put in a $10 bill. The delivery guy gets back to the pizza place and goes to pay the cashier for the pizza. The cashier tells him there has been a mistake and he should have only charged them $25. So the cashier gives the delivery guy back 5 $1 bills and tells him to take it back to the guys who bought the pizza. On the way back to the guys the delivery guy starts thinking that the 3 guys will have a hard time dividing the 5 $1 bills and they did not tip him. So he decided to keep $2 for himself and give them back each $1. So now each guy has paid $9 instead of $10

Now the problem. Each guy has now paid $9 and we know 9x3=27 and the delivery guy kept 2 and 27+2=29. WHAT HAPPENED TO THE OTHER DOLLAR?

Fu Manchu · Post by **Fu Manchu** » Tue Sep 17, 2002 11:39 am

Heres what i get lol.

3 guys order pizza = $30 --- $30 divided by 3 = $10/person

Pizza was only $25 --- so pizza man has to bring $5 back to 3guys

Pizza man decides to keep 2dollars

$5 - $2 = 3

$25 divided by 3 = $8.30

$9.00 -$8.30 = 70cents

70cents x 3 = $2.10 + $2 = $4.10 (pizza dude kept rest of the money is a tip because he did not get one)

$30 - $4.10 = $25.9

dadx2mj · Post by **dadx2mj** » Tue Sep 17, 2002 11:54 am

Delivery guy kept $2 not $2.10 and each guy paid $9 not $8.30

wvjohn · Post by **wvjohn** » Tue Sep 17, 2002 12:45 pm

30 pizza/3 = 10 bucks a guy

25/3 = 8.33 per guy

5 -2 = 3/3 = 1

8.33 +1 = 9.33 x3 = 28

28 + 2 = 30

dadx2mj · Post by **dadx2mj** » Tue Sep 17, 2002 12:55 pm

Both you guys are doing the same thing. If you go to the original story each guy paid $9 not $8.33 I understand how you are getting there but why wont the problem work out with only even dollars like in the original scenario?

succubiss · Post by **succubiss** » Tue Sep 17, 2002 3:13 pm

you're asking a question that doesn't make sense.

the delivery guy kept the $2 from the $27, not in addition to the $27.
you're supposed to add $2 to $25 to get $27.

So in essence the 3 guys paid $9 x 3 = $27 (after the refund).
from that amount, $25 went to the pizza store, and $2 went to the driver's pocket.

$27 - 2 = $25.
The original $30 does not come into play in the end figures and is used to confuse the issue

dadx2mj · Post by **dadx2mj** » Tue Sep 17, 2002 3:39 pm

The whole thing is based on them originally handing the delivery guy $30 and then trying to figure out where the $30 end up. To start with $30 and end up with $29 does not account for the original $30 and still leaves one dollar missing. I can follow all the logic that have been used in the answers given so far but you should be able to add the numbers in either direction and still account for $30 and for some reason it just does not work out.

Post by **sbp** » Tue Sep 17, 2002 3:53 pm

Yeah well while you guys are figuring out where the other dollar went, I ate the pizza. :lol

Busby · Post by **Busby** » Tue Sep 17, 2002 4:07 pm

The problem does make sense.

Each gives $10. But each gives $1 back. So they each effectively pay $9. So 9x3 = 27. The pizza guy kept $2 so the amount is $29.

Now as for what happened to the mysterious dollar.

25/3 = $8.33

8.33 + 1 = 9.33 - 9.00 = .33

.33 x 3 = .99

So in effect each guy actually payed $8.33 for the pizza but was given a dollar back so they paid $9.33 effectively. So if they all give a $10 bill and get a $1 back then they get $9, as established previously. So when the difference between the effective amount and the actual amount is .33 and .33 and .34 for each of the guys and when added together equal a dollar. This is a weird problem and I believe this explain its, could be completely wrong.

Fu Manchu · Post by **Fu Manchu** » Tue Sep 17, 2002 4:12 pm

its a simple problem .. its just missing some information and you have to figure out what that information is .. which is the acual tip the three guys gave the pizza dude ... not the 2 dollars he pocketed ... the three guys dont even know that he pocketed that cash

glassoftea · Post by **glassoftea** » Tue Sep 17, 2002 4:14 pm

You have to look at it from another veiwpoint.

All the money is there, they paid 27 dollars for the pizza, 25 of the 27 went to the cashier, 2 of the 27 went to the delivery boy. Now, he gave them back three dollars, one dollar each so the three he gave them plus the 27 they paid for the pizza equals 30 dollars. They each paid 1/3 of 27 dollars, not 9 dollars each.

30-30=30 thirty for pizza is what they paid
30-25= five dollars back to all three guys
5-3= one dollar each to each person
2= pizza guy kept

30-25=5-3-2=0

Read it a couple of times and forget about the 9 dollars each, that is where the trick is.

Now, what I want to know is what pizza guy would bring back anything? I'll bet very few!

glass

succubiss · Post by **succubiss** » Tue Sep 17, 2002 4:23 pm

Originally posted by Busby
The problem does make sense.

Each gives $10. But each gives $1 back. So they each effectively pay $9. So 9x3 = 27. The pizza guy kept $2 so the amount is $29.

Incorrect. $27 is the total amount they paid. $25 goes to store, $2 goes to driver.

----------

Explanation. From the original $30, who gets what?

$25 -> pizza store
$2 -> Tip
$3 -> refund

No fractions. Most people are assuming the store gets the whole $27 and they try to add the $2 tip to that, but you have to remember that the store only gets $25.

dadx2mj · Post by **dadx2mj** » Tue Sep 17, 2002 4:31 pm

I think glassoftea has the best answer. I still cant get over the feeling that we have a flaw in our mathematics system tho because you should be able to work it out any way and come up with the same answer. Or maybe there is just a play on words that I am not seeing.

Actually I think sbp had the best idea ....just eat the damn pizza and forget the dollar

Pugsley · Post by **Pugsley** » Tue Sep 17, 2002 7:01 pm

OK i got it all figured out....

The other dollar fell between the seat in the dilevery guys truck!!!

tunis5000 · Post by **tunis5000** » Tue Sep 17, 2002 7:13 pm

It's just math screwing with you. Remember, multiply and divide first, then add and subtract.

Or just read this: http://www.justriddlesandmore.com/missingsol.html