The ratio of two numbers is $10: 7$ and their difference is $105$. The sum of these numbers is

The value of $k$ that must be added to $7, 16, 43,$ and $79$ so that they are in proportion is

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

Marks of $X$ and $Y$ are in the ratio $3: 11$ respectively. If the marks of $X$ are $9$,then find the marks of $Y$.

The present ages of Reena and Usha are $24$ and $36$ years,respectively. What was the ratio between the ages of Usha and Reena $8$ years ago?

The number of students in three classes are in the ratio $2:3:4$. If $12$ students are increased in each class,this ratio changes to $8:11:14$. The total number of students in the three classes in the beginning was: