DAY 438

EASY AS 1, 2, 3.....
Credit: GAMES Magazine
May, 2001
Martin Gardner

There are just two ways to insert four plus or minus signs between the digits 123456789 to yield a sum of 1:

1 + 23 - 45 - 67 + 89 = 1
1 - 23 + 45 + 67 - 89 = 1

Curiously, the solutions are the same except that the signs are reversed.

Now see if you can insert four plus or minus signs in the sequence 987654321 to make a sum of 1. There is only one solution.

Answer:

98 - 76 - 54 + 32 + 1 = 1