## Matt71 3 years ago Using the digit 7 five time, place the basic arithmetic signs in between the digits to obtain a total of 540

1. pratu043

nice question.....

2. Matt71

I know, it's been driving me nuts

3. pratu043

can you join two 7s together to form 77?

4. Matt71

Nah, you gotta put the signs in between each one

5. Matt71

You're going crazy, aren't you?

6. Stom

this question is right r u sure?

7. Stom

because if it is not then bad things will happen

8. Matt71

Yeth, I'm pretty sure it's the question

9. Matt71

And now everyone's thinking...

10. nikhil389

It would be fast to do with computer code, any one good with programming ?

11. wasiqss

certainly question of the week

12. Stom

yes certainly

13. TuringTest

if it doesn't get solved here put it in the meta-math section for future reference

14. Matt71

I've really been trying this for a while and I think it's messed up anyone else think it's impossible?

15. Matt71

as in, it's total overload here

16. jimmyrep

i'm not sure if this fits the rules but 77 x 7 + (7 / 7) gives 540

17. TuringTest

+ - / and * only, right? no squaring or anything?

18. Ishaan94

concatenation isn't arithmetic right? nice work jimmyrep btw

19. Matt71

jimmyrep, if no one can find a solution without the placing two 7s together, I'll use your solution

20. jimmyrep

ok

21. pratu043

i don't think you can do it without joining two 7s together, jimmy rep has the right answer.

22. jimmyrep

77 is probably not allowed

23. wasiqss

jimmy rep yehh 77 not allowd

24. Matt71

It's probably not, but if it isn't I think it's impossible. I've been over this for over two hours, can't do anything to solve it. Yes, two hours, that's how obsessed I am with this question.

25. jimmyrep

these types of question are obsessive!

26. Matt71

Yep

27. pratu043

you can't do it because 540 is not divisible by 7.

28. Matt71

I KNEW IT! All that time wasted, I COULD'VE BEEN PLAYING TETRIS!

29. jimmyrep

lol

30. Matt71

Sweet baby turtles, I can't believe I missed that fact

31. TuringTest

that doesn't make a difference, you can make four 5's into 26 even though 26 is not divisible by 5 5*5+(5/5)

32. pratu043

Oh I see.....

33. moyo

in jimmy's example, he used 7/7 to add 1...

34. Matt71

Oh, yeah, then my time HASN't been a complete waste

35. Matt71

Good observation...

36. moyo

are parentheses allowed?

37. TuringTest

I would think so... it's just multiplication

38. Matt71

Yeah

39. moyo

i was thinking maybe there was an order of operations trick to solving it or something... grasping at straws :-)

You don't need them though, order of operations takes care of the problem above.

41. jimmyrep

yes - i didn't need the parenthesis

42. sandra

It all depends on if digits can be stacked without operations (is 77 valid?) - in which case 7*77+7/7 works as jimmyrep mentioned

43. Matt71

question y u no make sense? ლ(ಠ益ಠლ)

I feel like concatenation is needed here though. I'm not sure there's another way to grow the number fast enough while reserving 7/7 to make the difference of 1 you need to get to 540 itself.

45. wasiqss

this is certainly a crap question because 540 is not divisible by 7 and i advise ppl to stop wastin time on it

46. TuringTest

I already pointed out that the fact that 540 is not divisible by 7 makes no difference, read above

47. TuringTest

the problem is sitting in meta-math now, so it can be viewed in the future by someone who can figure this out, or prove it to be impossible.

48. Matt71

Sooooooo, you can't get a straight answer right?

49. TuringTest

not here, not now...

50. Tomas.A

51. Matt71

Bummer huh

52. Matt71

Oh, well, guys I don't want to completely waste all your time

53. Matt71

So, if everyone please get together with the plan and just randomly give everyone you can medals!

54. TuringTest

Like I say, check the meta-math section in the future, someone will probably either find the answer or prove it impossible... eventually.

55. Matt71

Thanks, to everyone, for all the help

56. Stom

what an awesome way to waste time

57. TuringTest

:)

58. Matt71

Well, medals or wasted time right? Might as well

59. Stom

but to prove it impossible without a computers help is going to be interesting

60. TuringTest

moneybird has a knack for this kind of thing, but he's not around.

61. Matt71

Yep, but it's gonna take a looot of time and luck

62. Matt71

Yeah, something about koalas that makes him as smart as he is

63. TuringTest

jejeje...

64. Stom

yo

65. Stom

why r ppl still on this question, u u ppl stil solving it?

66. TuringTest

I'm thinking it is impossible: adding 7/7=1 is the only way I can see to get to a number that is not divisible by 7, which only leaves three 7's left over, and the most we can make that into is 7*7*7=343 taking 540-(7/7)=539 and 539/7=77 hence it seems jimmyrep's answer is the only one possible, but I don't think this is a true proof that it is impossible.

67. Janie29

I tried a bunch of different ways, and I can't find an answer. Now I have a Chem Final in 45min., and this problem is all I'll be thinking of!

68. Tomas.A

JIMMY IS CORRECT :P