The third proportional to 38 and 15 is -

Answer: Option A

Let the third proportional to 38 and 15 be x
$$\begin{array}{rl}& \text{Then,}\\ & \Rightarrow 38:15::15:x\\ & \Rightarrow 38x=15\times 15\\ & \Rightarrow x=\frac{15\times 15}{38}\end{array}$$