Analysis: If a typhoon can affect point A, then the shortest distance between it and point A must be less than the typhoon radius. Because the typhoon moves to the southwest, point A is located in the west of 0, A and O, and the shortest distance point (point E) AOE between the typhoon and point A can form an equilateral right triangle.

Find the distance of AE first: the square of AO divided by 2 under the root sign (Pythagorean theorem) should be less than the typhoon radius.

Look at the picture. If the circle is a typhoon, then X to Y is the time period when A experiences typhoon, so find the distance of XY. (Pythagorean Theorem) Given AE and typhoon radius, you can use the stock purchase theorem to find AX or AY, then multiply it by 2 to get the distance of XY, and then set the formula (the distance of XY divided by 25km/h).

What you get is the result.