[Guest]

There is an interesting way of making 100 by using 1,2,3,4,5,6,7,8,9 (strictly in increasing order):

1 + 2 + 34 - 5 + 67 - 8 + 9 = 100

Another way of doing this is like this:

12 + 3 - 4 + 5 + 67 + 8 + 9 = 100

there are atleast 10 more ways(as far as I know..could be more).. using only + or - sign..(no decimals, no factorial, multiplication, division etc.)

Can you find all the ways?

12 + 3 + 4 + 5 - 6 - 7 + 89 = 100

[Guest]

123 - 4 - 5 - 6 - 7 + 8 - 9 = 100

for more I need more time

[Guest]

123+4-5+67-89=100

[Guest]

Assuming there can not be a "-" at the beginning.

1+23-4+56+7+8+9

12+3-4+5+67+8+9

1+2+34-5+67-8+9

1+2+3-4+5+6+78+9

123-4-5-6-7+8-9

123+45-67+8-9

1+23-4+5+6+78-9

12-3-4+5-6+7+89

12+3+4+5-6-7+89

123-45-67+89

123+4-5+67-89

[superprismatic]

I think that these are all 24 ways to make

100 following the instructions of the OP:

123-45-67+89

123+4-5+67-89

12-3-4+5-6+7+89

12+3+4+5-6-7+89

1+23-4+5+6+78-9

-1+2-3+4+5+6+78+9

1+2+3-4+5+6+78+9

123+45-67+8-9

1+2+34-5+67-8+9

12+3-4+5+67+8+9

1+23-4+56+7+8+9

123-4-5-6-7+8-9

123-45-67+89

123+4-5+67-89

12-3-4+5-6+7+89

12+3+4+5-6-7+89

1+23-4+5+6+78-9

-1+2-3+4+5+6+78+9

1+2+3-4+5+6+78+9

123+45-67+8-9

1+2+34-5+67-8+9

12+3-4+5+67+8+9

1+23-4+56+7+8+9

123-4-5-6-7+8-9

[superprismatic]

I think that these are all 24 ways to make

100 following the instructions of the OP:

123-45-67+89

123+4-5+67-89

12-3-4+5-6+7+89

12+3+4+5-6-7+89

1+23-4+5+6+78-9

-1+2-3+4+5+6+78+9

1+2+3-4+5+6+78+9

123+45-67+8-9

1+2+34-5+67-8+9

12+3-4+5+67+8+9

1+23-4+56+7+8+9

123-4-5-6-7+8-9

123-45-67+89

123+4-5+67-89

12-3-4+5-6+7+89

12+3+4+5-6-7+89

1+23-4+5+6+78-9

-1+2-3+4+5+6+78+9

1+2+3-4+5+6+78+9

123+45-67+8-9

1+2+34-5+67-8+9

12+3-4+5+67+8+9

1+23-4+56+7+8+9

123-4-5-6-7+8-9

I made the stupid mistake of having everything in there twice.

So, just take the first (or last) half of my answers.

[Guest]

There is an interesting way of making 100 by using 1,2,3,4,5,6,7,8,9 (strictly in increasing order):

1 + 2 + 34 - 5 + 67 - 8 + 9 = 100

Another way of doing this is like this:

12 + 3 - 4 + 5 + 67 + 8 + 9 = 100

there are atleast 10 more ways(as far as I know..could be more).. using only + or - sign..(no decimals, no factorial, multiplication, division etc.)

Can you find all the ways?

12 + 3 + 4 + 5 - 6 - 7 + 89 = 100

OK... now if decimals were allowed in between the digits, how can we make 100? use as many +, - and decimal points as you wish

[Guest]

0.1+23-4+5+67+8.9

.1-2+34-5-6+78.9

.1+2.3-4+5.6+7+89

1+2.3-4+5+6.7+89

Edited June 22, 2010 by kevink

[Guest]

Alright.. now what if the digits are reversed i.e. 987654321

one example:

98 + 7 - 6 + 5 - 4 + 3 - 2 - 1 = 100

use as many +,- signs and decimals points as you wish

[Guest]

98-7-6+5+4+3+2+1

9+8+76+5-4+3+2+1

98+7-6+5-4-3+2+1

-9-8+76-5+43+2+1

98+7-6-5+4+3-2+1

98-7+6+5-4+3-2+1

-9+8+7+65-4+32+1

9-8+76+54-32+1

98-7+6-5+4+3+2-1

9+8+76+5+4-3+2-1

98+7+6-5-4-3+2-1

9+87.6+5.4-3+2-1

98+7-6+5-4+3-2-1

98-7+6+5+4-3-2-1

9-8+7+65-4+32-1

0.9+87+6+5-4+3+2.1

0.9-8+76-5+4+32.1

9-8+76-5+4+3+21

-9+8+76+5-4+3+21

98-7-6-5-4+3+21

98-76+54+3+21