### The 5 Digit Code

Last winter I found myself locked out of my house because I couldn’t remember the 5 digits code to open the garage door. I used the following facts to get inside.

1. The second and third digits add up to 9.
2. The first digit is equal to the second digit cubed.
3. The sum of the third and fifth digits is the smallest number with exactly five divisors.
4. The fourth digit is equal to 6 times the second-to-last digit.
5. None of the digits repeat.

What was the code?

Last winter I found myself locked out of my house because I couldn’t remember the 5 digits code to open the garage door. I used the following facts to get inside. 1. The second and third digits add up to 9. 2. The first digit is equal to the second digit cubed. 3. The sum of…

### 1 2 3 4 5 6 7 8 9 = 100

This equation is incomplete: 1 2 3 4 5 6 7 8 9 = 100

One way to make it accurate is by adding seven plus and minus signs, for example.

1 + 2 + 3 – 4 + 5 + 6 + 78 + 9 = 100

How can you do it using only 3 plus or minus signs?

This equation is incomplete: 1 2 3 4 5 6 7 8 9 = 100 One way to make it accurate is by adding seven plus and minus signs, for example. 1 + 2 + 3 – 4 + 5 + 6 + 78 + 9 = 100 How can you do it using only…