June 2017

[R. Gerbicz]

There is a new Ibm puzzle:
https://www.research.ibm.com/haifa/p.../June2017.html

[Batalov]

Nice one! I think I have a "*" solution... (at least two)

[R. Gerbicz]

There is an update:

"Update (5/6): Division by zero is not allowed, but you can use non integers and unary minus (like the example above); and you get a '*' for every prime solution."

[Batalov]

Originally Posted by R. Gerbicz

There is an update:

"Update (5/6): Division by zero is not allowed, but you can use non integers and unary minus ..."

Instead of "non integers", he should have said "rationals". Or "fractions".
Or else we can do \(e^{i \pi}\) or something like \(\sqrt 4\).

Next month I am going to set up a webcrawler to watch the 'July2017.html' page
...so that I will not lose a couple hours to Robert ;-)

(This time I only learned of the problem launch from this thread.)

[uau]

Originally Posted by Batalov

Instead of "non integers", he should have said "rationals". Or "fractions".
Or else we can do \(e^{i \pi}\) or something like \(\sqrt 4\).

Not really. You can't insert arbitrary constants or operators into the expression (not integers or rationals either). The text only means that using the listed basic operators is allowed to create non-integer intermediate results (things like (1/3)*9 are allowed); allowing non-rational ones or not makes no difference as there are no operators which could create them.

[science_man_88]

Originally Posted by uau

Not really. You can't insert arbitrary constants or operators into the expression (not integers or rationals either). The text only means that using the listed basic operators is allowed to create non-integer intermediate results (things like (1/3)*9 are allowed); allowing non-rational ones or not makes no difference as there are no operators which could create them.

then the term to use was rational. A non-integer includes the complement of the integers under the complex numbers etc.

[LaurV]

grrr... another silly problem... the formulation is unclear, where and whenever you can/may/must place signs, and what's happening if you don't...

"while other seven-digit numbers simply cannot be solved, such as 0314157"

0+3-1+41+57=100

skip.

[uau]

Originally Posted by science_man_88

then the term to use was rational. A non-integer includes the complement of the integers under the complex numbers etc.

Nope. There is no limit to integers or any other particular class of intermediate results. Complex numbers would be allowed if the list of operators included any that produced them. Them being allowed just doesn't matter because there's no way to produce them.

[uau]

Originally Posted by LaurV

grrr... another silly problem... the formulation is unclear, where and whenever you can/may/must place signs, and what's happening if you don't...

"while other seven-digit numbers simply cannot be solved, such as 0314157"

0+3-1+41+57=100

skip.

I don't think it was unclear. Your "41 + 57" is quite clearly forbidden by the problem statement: "Without changing the order or concatenating two or more digits into a larger number".

[Batalov]

Originally Posted by LaurV

grrr... another silly problem... the formulation is unclear, where and whenever you can/may/must place signs, and what's happening if you don't...

"while other seven-digit numbers simply cannot be solved, such as 0314157"

0+3-1+41+57=100

skip.

Well, that part he explained just fine --

Without changing the order or concatenating two or more digits into a larger number, use the basic operations and parentheses so that the answer of the mathematical equation is exactly 100.

"Concatenating" is too long of a word? I though that you Romans invented this word, so it shouldn't be lost in translation for you?

[LaurV]

Whoooops...

Too fast a reading... the concatenated solution just jumped on my eyes from between the rows during I was skimming the text... Haha...

Ok, I will look for a solution and send one... to make it up. It may take a while, our algorithms are always slower than yours...