If the difference between the average of $x, y$ and $y, z$ is $12,$ then the difference between $x$ and $z$ is

The average of $6$ observations is $12$. $A$ new seventh observation is included and the new average is decreased by $1$. The seventh observation is

The average of first three numbers is double of the fourth number. If the average of all the four numbers is $12,$ find the $4^{th}$ number.

Average of $a, b$ and $c$ is $11$; average of $c, d$ and $e$ is $17$; average of $e$ and $f$ is $22$ and average of $e$ and $c$ is $17$. Find out the average of $a, b, c, d, e$ and $f$?

The average temperature of the first $4 \, \text{days}$ of a week is $38.6^{\circ} \text{C}$ and that of the last $4 \, \text{days}$ is $40.3^{\circ} \text{C}$. If the average temperature of the entire week is $39.1^{\circ} \text{C}$, find the temperature on the $4^{th} \, \text{day}$ (in $^{\circ} \text{C}$).

$A, B, C$ and $D$ are four consecutive odd numbers and their average is $42$. What is the product of $B$ and $D$?