Math Homework Help

[bunker]

This was for extra credit and we've already answered them all using good guesswork.
What I want to know is if there is a method to solving these.

She's given 5 numbers in a row and a solution and has to determine which operators to use to arrive at the solution with the given numbers.

Here's one example:

50 _ 4 _ 25 _ 5 _ 15 = 50

Fill in the blanks with either + - ÷ x

You can use any or all of the operators.
The numbers have to stay in that order.

As I said, I have the answers, I just want to know how to get them so I can better explain it to her.

Thanks!

Edit: I started writing a vbscript to figure this out, and I could easily do it but this is a 6th grade math assignment, I don't think the teacher intended them to write scripts to solve their problems!

Edit2: There will be no pics you perverted pedophiles, so don't even ask!

 

[Goosemaster]

Perhaps write out all the factors of each number and find out the relationships using smaller numbers

 

[giantpinkbunnyhead]

Hmm, that's gonna be hard to come up with. I think the best approach is logic and working backwards, but even then I don't know how far that would get you. Like, I know the last operator can't be a * because no integer times 15 makes 50. (Assuming we are restricted to integers?) That's the best I can come up with.

 

[2Xtreme21]

I honestly think the best way would be just guess/check. Rarely does higher level math make you do things like this. In fact, I can't think of any situation where I had to do stuff like this other than for fun / extra credit in elementary school.

 

[bunker]

Originally posted by: giantpinkbunnyhead
Hmm, that's gonna be hard to come up with. I think the best approach is logic and working backwards, but even then I don't know how far that would get you. Like, I know the last operator can't be a * because no integer times 15 makes 50. (Assuming we are restricted to integers?) That's the best I can come up with.

Nothing was said about being restricted to integers, then again, this is a 6th grade assignment so maybe that can be an assumption? None of the calculations for the 10 problems we did ended up with anything but integers though.

 

[KLin]

((50x4-25)/5)+15=50

 

[bunker]

Originally posted by: 2Xtreme21
I honestly think the best way would be just guess/check. Rarely does higher level math make you do things like this. In fact, I can't think of any situation where I had to do stuff like this other than for fun / extra credit in elementary school.

You may very well be correct that this was just a fun, take a guess, kind of thing.

 

[bunker]

Originally posted by: KLin
((50x4-25)/5)+15=50

Well yeah, but did you guess or use some kind of formula? And this problem and one other were the only ones that used all 4 operators, the rest ended up with combinations of them.

 

[Goosemaster]

Originally posted by: bunker

Originally posted by: giantpinkbunnyhead
Hmm, that's gonna be hard to come up with. I think the best approach is logic and working backwards, but even then I don't know how far that would get you. Like, I know the last operator can't be a * because no integer times 15 makes 50. (Assuming we are restricted to integers?) That's the best I can come up with.

Nothing was said about being restricted to integers, then again, this is a 6th grade assignment so maybe that can be an assumption? None of the calculations for the 10 problems we did ended up with anything but integers though.

I don't think they've thought them anything but basic decimals and fractions, so as far as they are concerned they probably only know the guess and check, substitution, and synthetic division methods...if even that

 

[mundane]

Guess/Check. It's a good exercise for them to learn order of operations. As for programmatic solution, brute force.