If the average of $6$ consecutive even numbers is $25 ,$ the difference between the largest and the smallest number is

A cricketer whose bowling average is $12.4$ runs per wicket takes $5$ wickets for $26$ runs and thereby decreases his average by $0.4$ The number of wickets taken by him till the last match was

The average weight of $21$ boys was recorded as $64 \,kg.$ If the weight of the teacher was added, the average increased by one $kg.$ What was the teacher's weight?

The average of marks obtained by $120$ candidates in a certain examination is $35 .$ If the average marks obtained by passed candidates are $39$ and those of the failed candidates are $15,$ then what is the number of candidates who passed the examination?

The average of $20$ numbers is $30$ and that of other $30$ numbers is $50 .$ What is the average of all the numbers.