Use the image to answer the question.

An illustration shows a 10 by 10 grid. A non-right triangle is enclosed within the grid. The first vertex is at the top of row 2 and the right of column 1. The second vertex is at the top of row 10 and the right of column 4. The third vertex is at the top of row 10 and the right of column 7.

What is the area of the non-right triangle? The base and height are found by counting the squares.

(1 point)
Responses

14 square units
14 square units

28 square units
28 square units

12 square units
12 square units

24 square units

1 answer

To find the area of the triangle formed by the given vertices, we can use the coordinates of the vertices and apply the formula for the area of a triangle using its vertices:

  1. Identify the vertices:

    • Vertex A (2, 1)
    • Vertex B (10, 4)
    • Vertex C (10, 7)
  2. Calculate the area using the determinant method: The formula for the area (A) of a triangle given vertices \((x_1, y_1)\), \((x_2, y_2)\), and \((x_3, y_3)\) is:

    \[ A = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right| \]

    Plugging in our vertex coordinates:

    \[ A = \frac{1}{2} \left| 2(4 - 7) + 10(7 - 1) + 10(1 - 4) \right| \]

    Simplifying this step by step:

    \[ = \frac{1}{2} \left| 2(-3) + 10(6) + 10(-3) \right| \]

    \[ = \frac{1}{2} \left| -6 + 60 - 30 \right| \]

    \[ = \frac{1}{2} \left| 24 \right| = \frac{24}{2} = 12 \]

Thus, the area of the triangle is 12 square units.

Therefore, the correct answer is: 12 square units.