The strength of a school increases and decreases in every alternate year by $10 \%$. It started with an increase in $2000$. Then the strength of the school in $2003$ as compared to that in $2000$ was

$A$ fruit seller had some apples. He sells $40 \%$ of the apples and still has $420$ apples. Originally,how many apples did he have?

For admission in a postgraduate program of Calcutta University,$90 \%$ of the candidates who appeared for the written test were males and the rest were females. $60 \%$ of the males and $80 \%$ of the females passed the written test. What is the total number of students who appeared for the written test,if the total number of passed candidates was $1240$?

An ore contains $23 \%$ copper. To get $69 \text{ kg}$ of copper, the quantity of the ore required is: (in $\text{ kg}$)

Rajiv spends $20 \%$ of his salary on food,$15 \%$ on conveyance,$10 \%$ on education,and $35 \%$ on house rent. If he spends $Rs. 1950$ on education,how much does he spend on conveyance?

In an examination,it is required to get $256$ of the total maximum aggregate marks to pass. $A$ student gets $192$ marks and is declared failed. The difference between the marks obtained by the student and the marks required to pass is $10 \%$. What are the maximum aggregate marks a student can get?