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Topic: make 100 by using 1, 7, 7, 7, 7
Replies: 41   Last Post: Nov 15, 2007 6:13 PM

 Messages: [ Previous | Next ]
 magidin@math.berkeley.edu Posts: 11,749 Registered: 12/4/04
Re: make 100 by using 1, 7, 7, 7, 7
Posted: Nov 13, 2007 11:57 AM

David W. Cantrell <DWCantrell@sigmaxi.net> wrote:
>amzoti <amzoti@gmail.com> wrote:
>> On Nov 13, 7:28 am, "Benjamin A. Bartsch"
>> <benjamin.a.bart...@gmail.com> wrote:

>> > dangerousgam...@gmail.com schrieb:
>> >

>> > > So, using only +, -, x, /, and parentheses, and ONLY these numbers:
>> >
>> > > 1, 7, 7, 7, 7
>> >
>> > > how can you make 100? Is there more than one solution?
>> >
>> > ---> (7+1/7)*7*(7/7+1)
>> >
>> > Benjamin

>>
>> That has five 7's and you are only allowed 4.

>
>Right. But I'm not sure that the "solution" 177 - 77 is legitimate either
>since it uses juxtaposition, which is not something which the OP mentioned
>that could be used.
>
>Here's a different solution which does not use juxtaposition:
>
>7 x 7 + 7 + 7 + 1

Using the usual precedence of operations, you have that this is equal
to (7x7) + 7 + 7 + 1, which comes out to 64.

I can't come up with any way to associate them to get 100, though:

[7 x (7+7)] + 7 + 1 = 106
[7 x (7+7+7)] + 1 = 148
7 x (7 + 7 + 7 + 1) = 154

So... how did you get 100?

--
======================================================================
"It's not denial. I'm just very selective about
what I accept as reality."
--- Calvin ("Calvin and Hobbes" by Bill Watterson)
======================================================================

Arturo Magidin
magidin-at-member-ams-org

Date Subject Author
11/12/07 dangerousgame95@gmail.com
11/12/07 Thomas Nordhaus
11/12/07 amzoti
11/12/07 quasi
11/12/07 dangerousgame95@gmail.com
11/13/07 magidin@math.berkeley.edu
11/12/07 Thomas Nordhaus
11/12/07 quasi
11/12/07 Joshua Cranmer
11/12/07 Raymond Manzoni
11/13/07 William Elliot
11/13/07 amzoti
11/12/07 David R Tribble
11/12/07 Nat Silver
11/12/07 Raymond Manzoni
11/12/07 Raymond Manzoni
11/13/07 benjamin.a.bartsch@gmail.com
11/13/07 amzoti
11/13/07 David W. Cantrell
11/13/07 magidin@math.berkeley.edu
11/13/07 David W. Cantrell
11/13/07 magidin@math.berkeley.edu
11/13/07 briggs@encompasserve.org
11/13/07 Robert Israel
11/13/07 Dave Seaman
11/13/07 benjamin.a.bartsch@gmail.com
11/13/07 amzoti
11/13/07 David W. Cantrell
11/13/07 Jan Kristian Haugland
11/13/07 Robert Israel
11/13/07 Kira Yamato
11/13/07 Kira Yamato
11/13/07 Robert Israel
11/13/07 amzoti
11/14/07 Thomas Nordhaus
11/15/07 Michael Press
11/14/07 Michael Press
11/15/07 Kira Yamato
11/15/07 Michael Press
11/15/07 Rick Decker
11/13/07 Raymond Manzoni