Question

A die is thrown 3 times and the sum of the thrown numbers    is 15. The probability for which the number 5 appears in first   throw is _______

(a) (3/10)

(b) (1/36)

(c) (1/9)

(d) (1/3)

Answer 1

The correct option (a) (3/10)

Explanation:

dice is thrown 3 times.

sum of numbers = 15

such triplets are {(3, 6, 6)(4, 5, 6)(4, 6, 5)(5, 5, 5)(5, 6, 4)(5, 4, 6)(6, 3, 6)(6, 6, 3)(6, 4, 5)(6, 5, 4)}

case in which 5 appears at 1^st place = {(5, 5, 5)(5, 6, 4)(5, 4, 6)}

∴ P(event) = (3/10).