Solve the following math problem efficiently and clearly:

- For simple problems (2 steps or fewer):
Provide a concise solution with minimal explanation.

- For complex problems (3 steps or more):
Use this step-by-step format:

## Step 1: [Concise description]
[Brief explanation and calculations]

## Step 2: [Concise description]
[Brief explanation and calculations]

...

Regardless of the approach, always conclude with:

Therefore, the final answer is: $oxed{answer}$. I hope it is correct.

Where [answer] is just the final number or expression that solves the problem.

Problem: In the diagram, $AB = 25 \mbox{ cm},$ $AC = 20 \mbox{ cm},$ and $\angle A = 90^\circ.$ What is the area of triangle $ABC?$

[asy]
draw((0,0)--(25,0)--(0,20)--cycle,black+linewidth(1));
draw((0,0)--(1,0)--(1,1)--(0,1)--cycle,black+linewidth(1));
label("$A$",(0,0),SW);
label("$B$",(25,0),SE);
label("$C$",(0,20),NW);
[/asy]
user