Hello, struck!

Code:

- Q *
: |
: 10t |
: |
80 B *
: | *
: | *
: 80-10t | * d
: | *
: | *
: | *
- O * - - - - - - * - - - - *
120-20t A 20t P
: - - - - 120 - - - - :

Motorbike starts at : .

In seconds, it moves m to point

. . Hence: .

Motorbike starts at : .

In seconds, it moves m to point

. . Hence: .

The distance between them is: .

And we wish to minimize

Note that, if we minimize , we will minimize

In right triangle

This simplifies to: . .[1]

The graph of this function is an up-opening parabola.

. . Its minimum is at its *vertex.*

The vertex is at: .

Substitute into [1]: .

Therefore: .