Question

Two unbiased coins whose faces are marked $1$ and $2$ are tossed. The mean value of the total of the numbers is

• A. $3$
• B. $4$
• C. $5$
• D. $2$

Answer 1

The correct option is A $3$

Probability of coin when it shows 1 $=P\left(1\right)=\frac{1}{2}$
Probability of coin when it shows 2 $=P\left(2\right)=\frac{1}{2}$
The mean value of the total of the numbers is $=1\times P\left(1\right)+2\times P\left(2\right)+1\times P\left(1\right)+2\times P\left(2\right)$
$=(1\times \frac{1}{2}+2\times \frac{1}{2})+(1\times \frac{1}{2}+2\times \frac{1}{2})$
$=3$