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Two dice are thrown together and the total score is noted. The events E, F and G are ‘a total of 4’, ‘a total of 9 or more’, and ‘a total divisible by 5’, respectively. Calculate P(E), P(F) and P(G) and decide which pairs of events, if any, are independent.

Answers (1)

Given-

Two dice are drawn together i.e. n(S)= 36

S is the sample space

E = a of total 4

F= a total of 9 or more

G= a total divisible by 5

Therefore, for E,

E = a of total 4

∴E = {(2,2), (3,1), (1,3)}


∴n(E) = 3

For F,

F= a total of 9 or more

∴ F = {(3,6), (6,3), (4,5), (5,4), (6,4), (4,6), (6,5), (6,6), (5,5), (5,6)}

∴n(F)=10

For G,

G = a total divisible by 5

∴ G = {(1,4), (4,1), (2,3), (3,2), (4,6), (6,4), (5,5)}
∴ n(G) = 7

Here, (E \cap F) = φ AND (E \cap G) = φ

Also, (F \cap G) = {(4,6), (6,4), (5,5)}
 \Rightarrow n (F \cap G) = 3 and (E \cap F \cap G) = φ

\\ P(E)=\frac{n(E)}{n(S)}=\frac{3}{36}=\frac{1}{12} \\ P(F)=\frac{n(F)}{n(S)}=\frac{10}{36}=\frac{5}{18} \\ P(G)=\frac{n(G)}{n(S)}=\frac{7}{36} \\ P(F \cap G)=\frac{3}{36}=\frac{1}{12} \\ P(F) \cdot P(G)=\frac{5}{18} \times \frac{7}{36}=\frac{35}{648}

Therefore,

P (F \cap G) ≠ P(F). P(G)

Hence, there is no pair which is independent

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infoexpert22

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