Right triangles and algebra: ACT Math Practice Question

Try this ACT math practice question on the topics of right triangles, algebraic translation and manipulation.

The perimeter of a right triangle is $18$ inches, and one of the legs of the triangle is $6$ inches long. How many inches longer is the hypotenuse than the length of the shortest leg ?

1. $\quad 1.5$
2. $\quad 2$
3. $\quad 3$
4. $\quad 3.5$
5. $\quad 4$

Choice C