What is the area of triangle QRS?

7 square units

9 square units

10 square units

13 square units

Circumscribing a rectangle around the triangle SQR, as shown in the figure, we see that the rectangle has dimensions 3 by 6, so its area is 18 square units.

We can also see that the area between the rectangle and the triangle SQR consists of 3 right triangles with dimensions 2 by 3; 6 by 2, and 1 by 4.

The area of there 3 triangles is (2*3) / 2 + (6*2) / 2 + (1*4) / 2 = 3+6+2=11.

Thus, the area of the triangle is what is left from removing the areas of the 3 surrounding triangles from the area of the rectangle:

A (SQR) = 18-11=7 (square units).

Answer: 7 square units