In an examination,it is required to multiply a number by $7$,but by mistake,a student divides it by $7$. What is the error percentage?

$A$ businessman imported laptops worth $Rs$ $210,000$,mobile phones worth $Rs$ $100,000$,and television sets worth $Rs$ $150,000$. He had to pay $10\%$ duty on laptops,$8\%$ on phones,and $5\%$ on television sets. How much total duty (in Rupees) did he have to pay on all items as per the above details?

In a class of $80$ students and $5$ teachers,each student received sweets equal to $15 \%$ of the total number of students,and each teacher received sweets equal to $25 \%$ of the total number of students. How many sweets were there in total?

Mr. Shamin's salary increases every year by $10 \%$ in June. If there is no other increase or reduction in the salary and his salary in June $2011$ was $Rs$ $22,385$,what was his salary in June $2009$?

If $40 \%$ of a number is equal to two-third of another number,what is the ratio of the first number to the second number?

$23 \%$ of $8040 + 42 \%$ of $545 = ? \%$ of $3000$