Question

A pair of dice is rolled again and again till a total of 5 or 7 is obtained

Answer 1

pair of dice is rolled n(s)=6c2
die is rolled again and again till we obtained 5or 7 n(a)=12c5×12c7
p(a)=n(a)/n(s)
=12c5×12c7/6c2
=12c5×12c5/6c2
=528/5