Here's a quick breakdown by cases (last digit must be 0 or 2 ): Last digit =0 First digit can be 1,2 or 3⇒3 choices The two middle places are filled by the remaining 2 digits in 2!=2 ways ⇒3×2=6 numbers Last digit =2 First digit can be 1 or 3 (can't be 0 or 2 ) ⇒2 choices The two middle places are filled by the remaining 2 digits in 2!=2 ways ⇒2×2=4 numbers Total =6+4=10.