Counting objects remaining.. noob question

Unity Engine
1

I thought that the gameObject.Find would work but it apparently just keeps counting and each time a new object enters and never subtracts when one leaves… So I tried to keep track of each ball that left play and subtract it from the Tagged objects that had been created but it seems there are a bunch of bugs this way as it sometimes miscounts…

I basically tried it each way I could so I decided to come here and have you all enlighten me on my mistake.

	void OnTriggerEnter( Collider other){
		Ball Ball = other.GetComponent<Ball> ();
		if (Ball) {
			ballsDead++;
			ballsLeft = GameObject.FindGameObjectsWithTag("ball").Length;
			Debug.Log(ballsLeft-ballsDead);

			if (ballsLeft-ballsDead <= 0){
			
			Ball.Die ();
			}
		}
	}
2

You want to know how many balls are in your trigger zone?

Try this: