P is a certain point on the fixed length line ab. it is known that ab = 30cm. C and d start from P and B and move to the left along the line AB at the speed of 1cm / s and 2cm / s respectively (C is on the line AP and D is on the line BP). 1. In the process of movement, there is always PD = 2Ac. Please explain the position of P on the line ab

P is a certain point on the fixed length line ab. it is known that ab = 30cm. C and d start from P and B and move to the left along the line AB at the speed of 1cm / s and 2cm / s respectively (C is on the line AP and D is on the line BP). 1. In the process of movement, there is always PD = 2Ac. Please explain the position of P on the line ab

Let the distance from point P to point a be xcm, and the movement timing be t:
Then PD = (30-x) - 2T
ac=x-t
According to PD = 2Ac,
（30-x）-2t=2（x-t）
We get x = 10
The distance between point P and point a is 10 cm