Simple riddle

  • Thread starter arcnets
  • Start date
  • #1
508
0
Hi, I'm the guy formerly known as carsten. This is just a test to see if everything works.
OK, you have the numbers
1 2 3 4 5 6 7 8 9 0.
You may insert some + signs and one = sign so to make a valid equation.
Like
12+34+5+6+78=90 (oops, false! )

Happy posting, and a big thanks to Greg who does a great job IMO.
 

Answers and Replies

  • #2
54
1
Easy ..
1+2+3+4+5+67+8=90 :smile:
 
  • #3
508
0
Yes. There's more solutions. :wink:
 
  • #4
drag
Science Advisor
1,062
0
1 + 2 + 3 + 4 + 56 + 7 + 8 + 9 = 90
12 + 3 + 45 + 6 + 7 + 8 + 9 = 90
 
  • #5
Njorl
Science Advisor
258
10
You used the 9's twice drag.

12+3+4+56+7+8=90
1+23+45+6+7+8=90
nothing =890
nothing=7890
etc.

Njorl
 
  • #6
Njorl
Science Advisor
258
10
If 2n-1 is prime, what can you say about (2n-1)*(2n-1)?

Njorl
 
  • #7
Ben-CS
Perfect!
 
  • #8
Njorl
Science Advisor
258
10
Absolutely. I thought that would take longer.

Njorl
 
  • #9
climbhi
Originally posted by Ben-CS
Perfect!
What do you mean perfect?
 
  • #10
Njorl
Science Advisor
258
10
A perfect number is equal to the sum of its factors. For this purpose, 1 is considered a factor, but the number itself is not.

Factors of 6 are 1,2,3 1+2+3=6
Factors of 28 are 1,2,4,7,14 1+2+4+7+14=28

6 and 28 are perfect.

Njorl
 

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