What is the length, in coordinate units, of the altitude from C to AB

What is the length, in coordinate units, of the altitude from C to AB in ΔABC shown in the standard (x,y) coordinate plane below?

  1. 3
  2. 5
  3. 6
  4. 10
  5. 13

Answer

The correct answer is A.

The length can be found by finding the positive difference in the y-coordinate at C, 4, and the y-coordinate of the point where the altitude intersects AB. All ordered pairs on AB have y-coordinate 1, so the length of the altitude is 4 - 1 = 3 coordinate units.