Question

A bag contains white,black and red balls only. A ball is drawn at random from the bag. The probability of getting a white ball is 3/10 and that of a black ball is 2/5. Find the probability of getting a red ball. if the bag contains 20 black balls then find the total no of balls in the bag

Answer 1

Bag has red, white and black balls
P( Of while ball) =P(W)= 3/10
P(of black ball) =P(B)=2/5
P(of red ball)=P(R)
we know P(R)+P(W)+P(B)=1
P(R)=1-P(W)-P(B)
P(R)=1-3/10-2/5
$= \frac{10 - 3 - 4}{10}$
$= \frac{3}{10}$
Black balls = 20
let total balls =x
$\frac{20}{x} = \frac{2}{5} \\ 50 = x = total \: balls$