What is the least number that must be added to $4042$ to make it a perfect square?

$\frac{6}{5}$ of $\frac{3}{4}$ of $\frac{1}{2}$ of $? = 3600$

The least number of five digits exactly divisible by $88$ is

$A$ boy added all natural numbers from $1$ to $12,$ however he added one number twice due to which the sum became $80.$ What is the number which he added twice?

What least number must be subtracted from $1294$ so that the remainder when divided by $9, 11, 13$ will leave in each case the same remainder $6$?

Natu and Buchku each have a certain number of oranges. Natu says to Buchku,"If you give me $10$ of your oranges,$I$ will have twice the number of oranges left with you." Buchku replies,"If you give me $10$ of your oranges,$I$ will have the same number of oranges as left with you." What is the number of oranges with Natu and Buchku respectively?