UPSC NDA Math Model Paper 8

If three fair coins are tossed then the different values of the number of heads we can get are 0, 1, 2 or 3 heads and the total number of different outcomes possible is 2 × 2 × 2 = 8.
p(0)=

‌3C0

8

=

1

8

p(1)=

‌3C1

8

=

3

8

p(2)=

‌3C2

8

=

3

8

p(3)=

‌3C3

8

=

1

8

∴E(Head)= Σ( Value × Probability )
=(0×

1

8

)+(1×

3

8

)+(2×

3

8

) +(3×

1

8

)
=

12

8

=1.5