Answer:
More clarification
Step-by-step explanation:
2 of a white ball =2/30 =1/15;
This is the probability of picking a black ball.
Let the number of black ball be X
x/(x +20)= 1/15[ probability of picking black ball ]
15x = x + 20 ; by cross multiplication
14x=20; x = 20/ 14 =1.42 = 1 [ approximately]
But to satisfy the premise given above; we have to approximate the no of balls to 2
