With an average speed of $40 \, km/h$,a train reaches its destination on time. If it goes with an average speed of $35 \, km/h$,it reaches late by $15 \, \text{minutes}$. The total journey is (in $km$):

$19$ persons went to a hotel for a combined dinner party. $13$ of them spent $Rs. 79$ each on their dinner and the rest spent $Rs. 4$ more than the average expenditure of all the $19$ persons. What was the total money spent by them?

It rained as much on Wednesday as on all the other days of the week combined. If the average rainfall for the whole week was $3 \, cm$,then how much did it rain on Wednesday? (in $cm$)

The average age of $80$ boys in a class is $15.$ The average age of a group of $15$ boys in the class is $16$ and the average age of another $25$ boys in the class is $14.$ What is the average age of the remaining boys in the class?

$A$ library has an average of $510$ visitors on Sundays and $240$ on other days. The average number of visitors per day in a month of $30$ days beginning with a Sunday is:

The average age of $x$ and $y$ is $20$ years. If $z$ were to replace $x$,the average would be $19$ and if $z$ were to replace $y$,the average would be $21$. Find the ages of $x, y$ and $z$.