wye configuration of resistors used as rf power divider

hi, i have a wye configuration that is used as a power divider, in each of the branches are 3 50ohms resistors connected in parallel. May i know the explanation as to why this value of resistor ? and why 3 of them connected in parallel ?

To keep the impedance seen by the source as 50 ohms. If you terminate the two outputs with 50 ohms then the input will still look like 50 ohms.

Resistive Power Splitters - Microwave Encyclopedia - Microwaves101.com

Keith.