Question

Three dice are thrown and a sum of 9 is obtained. Then the probability that the 3 dice show different numbers.

• A. 7/25
• B. 18/25
• C. 12/25
• D. 13/25

Answer 1

Answer: (B)

18/25

Answer 2

N(S) = no. of ways of throwing 9 with 3 dice.

= ⁸C₂ – 3 = 25

$\overline { \mathrm { E } }$ = {(1,4,4), (4,1,4), (4,4,1), (3,3,3), (2,2,5), (2,5,2), (5,2,2)

P( $\overline { \mathrm { E } }$ ) = $\frac { 7 } { 25 }$ ; P(5) = $\frac { 18 } { 25 }$.