Question

If points (5, 5), (10, k) and (–5, 1) are collinear, then k =

• A. 3
• B. 5
• C. 7
• D. 9

Answer 1

Answer: (C)

7

Answer 2

Area of triangle = 0

̃ $\frac{1}{2}$ [5(K – 1) + 10 (1 – 5) – 5 (5 – k)] = 0

̃ $\frac{1}{2}$ [5k – 5 – 40 – 25 + 5k) = 0

̃ k = 7