Question

Q.21 A box contains 25 balls. 7 balls are red, 10 balls are white and remaining are black. Find
the probability of getting
(i) a black ball
(ii) not a white ball
​

Answer 1

$\large{\underline{\underline \textsf{\color{red}{SOLUTION :}}}}$

$\: \: \: \:$

Here there are total 25 balls in a box , out of which 7 balls are red , 10 balls are white and the remaining balls i.e 25 - 17 = 8 , 8 balls are black.

$\sf \implies {n( S ) = 25}$

$\: \: \: \:$

1) Let A be the event of getting a black ball .

$\sf \implies{n ( A ) = 8}$

Now , P ( A ) = $\large \sf \frac{n ( A ) }{n ( S )} = \frac{8}{25}$

$\: \: \: \:$

2) Let B be the event of getting not a white ball .

( That is , red and black balls = 7 + 8 = 15 )

$\sf \implies{n( B ) = 15}$

Now , P ( B) = $\large \sf \frac{n (B ) }{n ( S ) } = \frac{15}{25 } = \frac{3}{5}$

$\: \: \: \:$

Therefore , The probability of getting a black ball is$\large \sf\frac{8}{25}$ and the probability of getting not a white ball is$\large \sf \ \frac{3}{5}$ .