what is the meaning of this symbol∝
The symbol means proportional. Refer to the link given below to know about it :
https://www.meritnation.com/ask-answer/question/what-is-the-meaning-of-proportional-plz-explain-with-an-e/physical-world/4313646
https://www.meritnation.com/ask-answer/question/what-is-the-meaning-of-proportional-plz-explain-with-an-e/physical-world/4313646