Question

I am playing a walking game with myself. On move 1, I do nothing, but on move n where 2 \le n \le 25, I take one step forward if n is prime and two steps backwards if the number is composite. After all 25 moves, I stop and walk back to my original starting point. How many steps long is my walk back?

Answer 1

21 steps

Explanation:

There are 9 prime numbers and 15 composite numbers between 2 and 25. So, a prime number would be 1 step forward, and a composite number would be 2 steps back.

`1*9+(-2)*15=9-30=-21`

We then take the absolute value of -21 to get 21 as our answer.

Hope this helped! :)