Question

a bag contain white black and red balls and aball is drawn a white ball is 3/10and of. black is2/5so find the probability of getting a red ball if the bag contain 20black ball then find the no of total ball

Answer 1

let red balls contain x and white balls contain y

so,
probability of white balls = y /(20+x+y)=3/10

10y=60+3(x+y)
7y-3x=60 --------------(1)

again probability of black balls =20/(x+y+20) = 2/5

100=2 (x+y)+40
x+y=30 ----------------(2)

solve equation (1 ) and (2)
y=15 and x =15

so, probability of red balls =15/50=3/10

and total balls =15+15+20=50