Question

A bag contains white black and red balls only a ball is drawn at random from the bag if the probability of getting a white ball is 3 divided by 10 and that of black ball is 2 divide by 5 then find the total number of balls in the bag.

Answer 1

Answer:

15

Step-by-step explanation:

Let the no of white balls be = x

Let the no of red balls be = y

number of balls black balls =20

total number of balls =x+y+20

Probability of getting a white ball =310

xx+y+20=310

=> 10x=3x+3y+60

=> 7x−3y=60

------(1)

Probability of getting a blind ball =25

(i.e)20x+y+20=25

= 100=2x+2y+40

=> 2x+2y=60

or x=y=30

----------(2)

Solving (1) and (2) we get,

7x−3y=60

x+y=30

______________

7x−3y=60

7x+7y=210

________________

−10y=150

=> y=15

x=15

Answer : 15

Answer 2

if we assume that total number of balls are 10

then, probability of white ball is 3/10

and, probability of black ball is 2/5=>4/10

and probability of red ball = (3/10)+(4/10)= 3/10

hence, our contradiction is right .
therefore, total number of ball in bag are 10.