Introduction

This puzzle challenges you to insert plus and minus signs between the digits 1, 2, 3, 4, 5, 6, 7, 8, and 9 to form an expression that equals 100. The digits must remain in order, but can be grouped into multi-digit numbers.

Solution

One effective solution is: 123 - 45 - 67 + 89 = 100. Let's verify: 123 minus 45 is 78, 78 minus 67 is 11, and 11 plus 89 equals 100. This approach uses subtraction to offset the sum and addition to reach the target.

Why It Works

By combining digits into larger numbers, we manipulate the overall value. Here, 123, 45, 67, and 89 are formed, and the operators balance the equation perfectly.