Question

a basket contains some black, 4 red and 5 green balls. If one ball is taken randomly, the probability of getting a green colour ball is 1/3. What is the no. of Black balls in the basket ? give answer with explanation.
Options are :-
A)3
B)4
C)5
D)6​

Answer 1

Answer:

If I pick the red ball first and the black one next we have a probability of 59×12=518 ( 12 because after I draw the red ball there are exactly 4 red and 4 black balls in the box, so the chance to draw a black one is 48 or 12 simplefied).

If I pick the black ball first the probability is 49×58=518 .

Combining these two probabilities we get 518+518=59

And other way to see it is this: the chance to pick two red ones is 518 (see the calculation above) the chance of picking two black ones is 49×38=16

And 1−(518+16)=59

Answer 2

Answer: 4/5.

Step-by-step explanation:Given the bag contains 2 red balls , 3 blue balls and 5 green balls.

Probability of getting a red ball is

2/10 = 1/5

But we need probability of not getting a red ball

Probability of not getting a red ball = 1 - probability of getting a red ball.

i.e., 1 - 1/5

= 4/5

Hence the probability of not getting a red ball is 4/5.