Question

What is the value of x? A. 2 Units B. 3 Units C. 5 Units D. 8 Units

Answer 1

You need the formula for geometric mean for right triangles as it applies to the altitude. For us, that formula will be $\frac{BD}{AD}=\frac{CD}{BD}$ where BD is your altitude. The formula then, filled in accordingly, would be $\frac{10}{x}=\frac{4x}{10}$. We cross multiply to get that $4x^2=100$. Divide both sides by 4 to get $x^2=25$, so x = 5. Choice C is the one you want.