DAY 72

Comment

It is fairly obvious that if P moves towards R, say, the area decreases, and that if P moves towards the top left corner of the board the area increases. So what movement will leave the area unchanged?
It might help to focus on the area of triangle PQR and to think of QS as the base. Moving P will not affect this base, but it might affect the height of the triangle.

Answer

Move P in a direction parallel to the line QS.

Readers' methods

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