Math Quiz

[CameronBornAndBred]

A friend sent me an email with a wicked math problem, and I don't have the answer. He included an Excel file, but it is too large to upload here, so let me know your answers and I'll let y'all know the winner. The Excel file is password protected, and the password is the answer. Since I haven't been able to open it yet, I haven't been right yet. I've googled the question, and tons of people have guessed wrong and none have guessed right (as far as I know). Here is the problem...

This is a 5th grade math problem. If you can open the spreadsheet, you'll see it's a very small list of people who have gotten the correct number. This is not a trick question. This is a real math problem so don't say that a bus has no legs.

There are 7 girls in a bus.
Each girl has 7 backpacks.
In each backpack, there are 7 big cats.
For every big cat there are 7 little cats.

Question: How many legs are there in the bus (not including the bus driver) ?
(The number of legs is the password to unlock the Excel sheet. If you open it, add your name and send it on to see who else can unlock it.)

[DukieInKansas]

Is 14 the correct answer?

[Turk]

Not to be a wet blanket - but be careful with that Excel file. That's a good way to spread viruses. If it were me, I'd explicitly update my virus defs and scan that file before doing anything with it...

[hamster]

Is 14 the correct answer?

I would think so - nothing says the cats are on the bus.

[CameronBornAndBred]

Not to be a wet blanket - but be careful with that Excel file. That's a good way to spread viruses. If it were me, I'd explicitly update my virus defs and scan that file before doing anything with it...
I've checked it.

[CameronBornAndBred]

Is 14 the correct answer?
That was my first guess, but no.

[Bostondevil]

You say this isn't a trick question, so, may we assume that the cats are on the bus? Also, may we assume that the cats have 4 legs a piece?

[Acymetric]

Is it 10,990? Thats what I came up with.

Edit: The only other thing it could be is 10,992, as far as I can tell. Or I'm completely wrong. Only time will tell.

[pfrduke]

You say this isn't a trick question, so, may we assume that the cats are on the bus? Also, may we assume that the cats have 4 legs a piece?

If this isn't a trick question, it's 10,990

7 girls X 2 legs = 14
7 big cats x 4 legs x 7 backpacks x 7 girls = 1372
7 little cats x 4 legs x 7 big cats x 7 backpacks x 7 girls = 9604

14 + 1372 + 9604 = 10,990

As an aside, though - 56 cats in each backpack??? Yikes!

[CameronBornAndBred]

BostonDevil has gotten it correct. I'm tempted to let people keep at it since she didn't post her answer. But a couple others have gotten it as well, so the correct number that unlocked the file (virus free) is 10,990.

I sure am happy that y'all's math is better than mine.

The one google answer that made me laugh hardest was a much lower number "because cats don't have legs".

[pfrduke]

BostonDevil has gotten it correct. I'm tempted to let people keep at it since she didn't post her answer. But a couple others have gotten it as well, so the correct number that unlocked the file (virus free) is 10,990.

I sure am happy that y'all's math is better than mine.

The one google answer that made me laugh hardest was a much lower number "because cats don't have legs".

I mean no disrespect by this, but why was this hard? Were people forgetting to include the 14 legs for the girls? Or were people just not getting the right number of 7's in the multiplication?

Also, what was in the spreadsheet?

[hughgs]

I mean no disrespect by this, but why was this hard? Were people forgetting to include the 14 legs for the girls? Or were people just not getting the right number of 7's in the multiplication?

Also, what was in the spreadsheet?

Two issues with the problem. First the number of cats. I suspect most people just assumed that there were 49 cats in each backpack when in reality there were 56. The second issue would be the girls. After getting wrapped up in the cats one could easily forget the girls or forget that girls have only two legs.

[CameronBornAndBred]

I was working under the 49 cat number. The excel file is basically a big illustration of visually how it works out. Unfortunately I can't shrink it enough to attach but you can download it here. http://wagnerwatercolor.com/images/Math_question.xls

[AtlBluRew]

As an aside, though - 56 cats in each backpack??? Yikes!

They must have been Hello Kitty backpacks.

[DukieInKansas]

I would think so - nothing says the cats are on the bus.

That was my thinking, also.

[snowdenscold]

I got 10,990.

[ ( 7^4 + 7^3 ) * 4 ] + [ 7^1 * 2 ]

Yes, I know I didn't need the []'s :)

[DukieInKansas]

As an aside, though - 56 cats in each backpack??? Yikes!

And how did those girls carry the 7 backpacks?

[Deslok]

Well, since we are asking math questions...

How many gifts are given in the song the 12 days of Christmas?


And btw, as a math teacher, I'd be embarrassed if the most of my kids couldn't answer that question correctly.

[DukieInKansas]

Well, since we are asking math questions...

How many gifts are given in the song the 12 days of Christmas?


And btw, as a math teacher, I'd be embarrassed if the most of my kids couldn't answer that question correctly.

I'll go out on a limb - 364

[OZZIE4DUKE]

Well, since we are asking math questions...

How many gifts are given in the song the 12 days of Christmas?


And btw, as a math teacher, I'd be embarrassed if the most of my kids couldn't answer that question correctly.

Hey Des! Great seeing you on Saturday. Amazing how small the Meadowlands is.

You temporarily need to change your location until it is time to return.

[Ben63]

Well, since we are asking math questions...

How many gifts are given in the song the 12 days of Christmas?


And btw, as a math teacher, I'd be embarrassed if the most of my kids couldn't answer that question correctly.

364. I sat here an figured it out, but I'm sure there is some fancy math symbol or method that could do it much easier than I did. Anyone?

[pfrduke]

I'll go out on a limb - 364

Pretty sure that's correct.

[OZZIE4DUKE]

364. I sat here an figured it out, but I'm sure there is some fancy math symbol or method that could do it much easier than I did. Anyone?

Yup. 364.

[snowdenscold]

364. I sat here an figured it out, but I'm sure there is some fancy math symbol or method that could do it much easier than I did. Anyone?

Sum ( Sum ( i, i=1...n) , n=1...12)

=

Sum ( n(n+1)/2 , n = 1...12)

Not really sure how to rewrite the second step into a formula...

[darthur]

Sum ( n(n+1)/2 , n = 1...12)

Not really sure how to rewrite the second step into a formula...


Break this into (1^2 + 2^2 + ... + 12^2) / 2 + (1 + 2 + ... + 12) / 2. As you said, the formula for the second is 12*(12+1)/4 = 39. The formula for the first is 12*(12+1)*(2*12+1)/12 = 325.

If there were n days of Christmas, the total number of gifts would be n*(n+1)*(n+2)/6.

[ArkieDukie]

A friend sent me an email with a wicked math problem, and I don't have the answer. He included an Excel file, but it is too large to upload here, so let me know your answers and I'll let y'all know the winner. The Excel file is password protected, and the password is the answer. Since I haven't been able to open it yet, I haven't been right yet. I've googled the question, and tons of people have guessed wrong and none have guessed right (as far as I know). Here is the problem...

This is a 5th grade math problem. If you can open the spreadsheet, you'll see it's a very small list of people who have gotten the correct number. This is not a trick question. This is a real math problem so don't say that a bus has no legs.

There are 7 girls in a bus.
Each girl has 7 backpacks.
In each backpack, there are 7 big cats.
For every big cat there are 7 little cats.

Question: How many legs are there in the bus (not including the bus driver) ?
(The number of legs is the password to unlock the Excel sheet. If you open it, add your name and send it on to see who else can unlock it.)

I like stuff like this, so I won't read ahead until after I take a stab at it. Each cat has 4 legs. For the little cats, there would be 7x7x7x7x4 (9604). For the big cats, 7x7x7x4 (1372). For the girls, 7x2 (14). Add 'em all up and you get 10,990. Is this right, or is it one of those annoying "As I was going to St. Ives" word play type problems?

[snowdenscold]

Break this into (1^2 + 2^2 + ... + 12^2) / 2 + (1 + 2 + ... + 12) / 2. As you said, the formula for the second is 12*(12+1)/4 = 39. The formula for the first is 12*(12+1)*(2*12+1)/12 = 325.

If there were n days of Christmas, the total number of gifts would be n*(n+1)*(n+2)/6.

Wow, I feel dumb now - though it has been awhile since high school math. I totally forgot to break n(n+1)/2 out into 2 separate sums.

Then it's just 1/2 * [Sum(i, i=1..n) + Sum(i^2, i=1..n)]

so 1/2 * [n(n+1)/2 + n(n+1)(2n+1)/6] = 1/2*1/6*[3n(n+1) + (2n+1)n(n+1)] = 1/2*1/6[(2n+4)n(n+1)]

= 1/2*1/6* [ 2n^3 + 6n^2+4n ] = 1/6*[n(n^2+3n+2)] = 1/6*[n(n+1)(n+2)].

That's one dedicated 'true love'...

[dukemomLA]

The 7 girls have 14 legs.

The big cats have 4 legs -- thus 28

The little cats have 4 legs - thus 28

So IMHO -- the answer is 70

Please let me know how stupid I am. Thanks

[dukemomLA]

The 7 girls have 14 legs.

The big cats have 4 legs -- thus 28

The little cats have 4 legs - thus 28

So IMHO -- the answer is 80

Please let me know how stupid I am. Thanks

[snowdenscold]

Wow, I feel dumb now - though it has been awhile since high school math. I totally forgot to break n(n+1)/2 out into 2 separate sums.

Then it's just 1/2 * [Sum(i, i=1..n) + Sum(i^2, i=1..n)]

so 1/2 * [n(n+1)/2 + n(n+1)(2n+1)/6] = 1/2*1/6*[3n(n+1) + (2n+1)n(n+1)] = 1/2*1/6[(2n+4)n(n+1)]

= 1/2*1/6* [ 2n^3 + 6n^2+4n ] = 1/6*[n(n^2+3n+2)] = 1/6*[n(n+1)(n+2)].

That's one dedicated 'true love'...

Wow, I made that much more complicated than it needed to be.... you could just go from the last expression in my second line straight to the answer by factoring out the 2 from that middle term and canceling it w/ the 1/2. So ignore that whole 3rd line.

[Deslok]

I'll go out on a limb - 364

That would indeed be the correct answer. Surprised I didn't get anyone to say 78(the number of gifts given on the last day).

[CameronBornAndBred]

On the last day of Christmas true loves brings the 36th goose a laying. I'd be pretty ticked off at sweetie pie for sticking me with all the eggs and goose poop.

[DukieInKansas]

On the last day of Christmas true loves brings the 36th goose a laying. I'd be pretty ticked off at sweetie pie for sticking me with all the eggs and goose poop.

What about the possibility that one of those geese lays golden eggs? Would that make it better?

[Deslok]

On the last day of Christmas true loves brings the 36th goose a laying. I'd be pretty ticked off at sweetie pie for sticking me with all the eggs and goose poop.

I think this (http://www.kraftmstr.com/christmas/humor/12days-h.html) is the appropriate link for that thought.

[CameronBornAndBred]

What about the possibility that one of those geese lays golden eggs? Would that make it better?
Yeah, that would help. I'd also give a few the 32 maids some mops and have them clean up a bit. Do each of the milk maids come with their own cow? If so, I'm moving. I'm not staying in a house with all the goose poop and cow patties.

[snowdenscold]

On the last day of Christmas true loves brings the 36th goose a laying. I'd be pretty ticked off at sweetie pie for sticking me with all the eggs and goose poop.

Actually 42 geese - even better! :D

[DukieInKansas]

And those 12 days of Christmas would set your true love back a mere $86,609 this year. (up from $78,100 last year.)