The average speed of a cyclist who covers first, second and third km at $20,16$ and $12\, km / hr$ respectively ( in $km / hr )$ is

The average of $X_{1}, X_{2}$ and $X_{3}$ is $14 .$ Twice the sum of $X_{2}$ and $X_{3}$ is $30 .$ What is the value of $X_{1} ?$

Mr. Patel walked $6\,km$ to reach the station from his house, then he boarded a train whose average speed was $60 \,km / hr$ and thus he reached his destination. In this way he took total of $3\, hours.$ If the average speed of the entire journey was $32\, km / hr$ then the average speed of walking is (in $km/hr$)

The average age of a graph of $9$ students is $20\, years.$ When $6$ more students joined the group, the average age falls by $2\, years.$ Then the average age of new students is

The average weight of $3$ men $A, B$ and $C$ is $84 \,k g .$ Another man, $D,$ joins the group, and the average weight becomes $80\, kg .$ If another man, $E$, whose weight is $3 \,kg$ more than that of $D ,$ replaces $A$, then average weight of $B , C , D$ and $E$ becomes $79 \,kg$. The weight of $A$ is (in $kg$)