$3.5$ can be expressed in terms of percentage as

What percentage of numbers from $1$ to $70$ have squares that end in the digit $1$?

An army lost $10 \%$ of its men in war,$10 \%$ of the remaining died due to disease,and $10 \%$ of the rest were declared disabled. Thus,the strength of the army was reduced to $7,29,000$ active men. What was the original strength of the army?

$860 \%$ of $50 + 50 \%$ of $860 = ?$

In an examination,$35 \%$ of the students passed and $455$ failed. How many students appeared for the examination?

The population of a town increases by $2.5 \%$ annually but decreases by $0.5 \%$ every year due to migration. What will be the net percentage increase in population after $2$ years (in $\%$)?