JEE Advanced Model Paper 5 with solutions for online practice

Answer (A, C)The different type of outcomes are possibleas: aaaa, aaab, aabb, abcc or abcd.
i.e. n(S) =

6

‌

C1 + 2 .

6

‌

C2 + 3 .

6

‌

C3 +

6

‌

C4
= 126
Probability that all four outcomes are different =

15

126

=

5

42

Probability that all four outcomes are alike =

6

126

=

1

21

Number of ways when outcomes are prime
n(E) =

3

‌

C1 + 2 .

3

‌

C2 +

3

‌

C2 + 3 .

3

‌

C3 = 15
∴ Probability that all four outcomes are primenumbers
=

15

126

=

5

42