Question

If 7 more green balls are put in the bag, the probability of drawing a green ball is now double of what it was before. Find .

Answer 1

Probability of black balls =  

20

x

​  

 

Probability of black balls after adding 10 new balls =  

30

x+10

​  

 

According to the question

=  

30

x+10

​  

=  

20

2x

​  

 

20x+200=60x

⇒40x=200⇒x=5