Question

A box contains 3 white and 4 black balls. Two balls are drawn randomly, which is the probability that either both are white or both are black balls

Answer 1

Answer:

total no of balls = 7

probability of getting a white ball, p(w) = 3/7

probability of getting a black ball ,p(b) = 4/7

probability that both are either white or black= p(w) p(w) +p(b) p(b) = 3/7×3/7 + 4/7×4/7= 25/49

Answer 2

Question

A box contains 3 white and black balls. Two balls are drawn randomly, which is the probability that either both are white or both are black balls

Given

• A box contains 3 white and black balls.
• Two balls are randomly drawn.

Required to Find

which is the probability that either both are white or both are black balls.

Solution

probably if drawing black in the first draw

$\sf = \frac{toal \: black \: balls}{tital \: balls} = \frac{2}{5}$

$\sf \: probably \: of \: drawing \: black \: in \: the \: second \: draw = \frac{1}{4}$

probability that both balls are black = probability of first ball being black × probability of second ball being black

$\sf = \frac{2}{5} \times \frac{1}{4}$

$\sf = \frac{1}{10}$