其它
What is the smallest whole number larger than the perimeter of any triangle with a side of length $9$ and a side of length $1$? (adapted from 2015 AMC8, Question 8) 
Overseas Competition->Knowledge Point->Calculation Modules->Basic Concepts of Equation->Inequalities
We know from the triangle inequality that the last side, $s$, fulfills $s\textless9+1=10$. Adding $9+1$ to both sides of the inequality, we get $s+9+1\textless20$, and because $s+9+1$ is the perimeter of our triangle, (C) 20 is our answer. 