What is the value of $68 \%$ of two-fifths of $550$?

The present ages of $A$ and $B$ are in the ratio $5:6$ respectively. After seven years,this ratio becomes $6:7$. Then the present age of $A$ in years is:

At present,the ratio between the ages of Arun and Deepak is $4:3$. After $6$ years,Arun's age will be $26$ years. What is the age (in years) of Deepak at present?

$A$ and $B$ together have ₹ $1210$. If $\frac{4}{15}$ of $A$'s amount is equal to $\frac{2}{5}$ of $B$'s amount,how much amount (in ₹) does $B$ have?

If $A: B = 2: 5$,$B: C = 4: 3$,and $C: D = 2: 1$,what is the value of $A: C: D$?

There is $1000 \, \text{litres}$ of milk in a pot. $100 \, \text{litres}$ of milk is taken out and the same amount of water is poured into it. Again, $200 \, \text{litres}$ of the mixture is taken out and the same amount of water is poured into it, and finally, $400 \, \text{litres}$ of the mixture is taken out and the same amount of water is poured into it. What is the amount of milk in the resulting mixture?