Question

An urn contains 7 red balls, 18 blue balls and 15 green balls. A ball is selected and its color is noted and then it is placed back to the urn. A second ball is selected and its color is noted. Find the probability of that both balls has the same color.
A. 0.1575
B. 0.3738
C. 0.3750
D. 0.1750

Answer 1

solution;

classification of ball that contain in the bag as follows:

red balls =    7

green balls = 15

blue balls ==18

total =         40 balls

so let R1 be the event of drawing red ball in first draw and R2 drawing red in second draw

G1 drawing green in first draw and G2 drawing green in second draw

B1 drawing blue in first draw and B2 drawing blue in the second draw

we have to find the probability that both drawing balls have the same color

so required probability = P(R1,R2) or P(G1,G2) or P(B1,B2)

P(R1, R2) = 7/40 * 7/40

P(G1,G2) = 15/40*15/40

P(B1,B2) = 18/40*18/40

so probability that both ball of the same color will be =

so answer is

B : 0.3738