The average of $30$ numbers is $15 .$ The average of the first $18$ numbers is $10$ and that of the next $11$ numbers is $20 .$ The last number is

$30$ pens and $75$ pencil altogether were purchased for $Rs.\, 510.$ If the average price of $75$ pencil was $Rs.\, 2$ , then what was the average price of a pen? (in $Rs.$)

The average of marks obtained by $150$ candidates in a certain examination is $50 .$ If the average marks of passed candidates is $55$ and that of the failed candidates is $25,$ what is the number of candidates who passed the examination?

David obtained $76,65,82,67$ and $85 \,marks$ (out of $100$ ) in English, Mathematics, Physics, Chemistry and Biology. What is his average $marks$ ?

The arithmetic mean of the following numbers is $1,2,2,3,3,3,4,4,4,4,5,5,5,5,5,6,6,6,6,6,6,7,7,7,7,7,7,7$

The batting aterage for $40$ innings of a cricketer is $50$ nuns. His highest score exceeds his lowest score by $172$ runs. If these two innings are excluded, the average of the remaining $38$ innings is $48$ runs. The highest score of the player is