A bag contains 5 black balls, 4 white balls and 3 red balls. If a ball is selected randomwise the probability that it is black or red ball is a. 1/3 b. 1/4 c. /12 d. 2/3

Options

A. `1//3`
B. `1//4`
C. `5//12`
D. `2//3`

Answer

D

Explanation

P ( selecting a black ball ) = ` ( ""^5C _ 1 ) /( ""^ 12 C _ 1 ) `
P ( selecting a red ball ) = `(""^ 3 C _ 1 ) /( "" 12 C _ 1 ) `
P ( black ball or red ball) = ` ( ""^5 C _ 1 + ""^ 3 C _ 1 ) /( ""^ 12 C _ 1 ) `
` = ( 8 ) /( 12 ) = ( 2 ) /( 3 ) `