Calculate the fourth proportional to the numbers $286, 78, 1342$.

If $(x+y):(x-y)=11:1$,find the value of $\frac{(5x+3y)}{(x-2y)}$.

When wheat is ₹ $13$ per $kg$,$75$ men can be fed for $15$ $days$ at a certain cost. How many men can be fed for $45$ $days$ at the same cost,when wheat is ₹ $1$ per $kg$?

If $A: B = 3: 4$ and $B: C = 8: 9$,then find the value of $A: B: C$.

The salaries of $A, B, C$ are in the ratio $2: 3: 5$. If increments of $15\%, 10\%,$ and $20\%$ are allowed respectively in their salaries,then what will be the new ratio of their salaries?

In a college,$150$ students of $MBA$ are enrolled. The ratio of boys to girls is $7:8$. There are three disciplines in the college: Marketing,$HR$,and Finance. In the Marketing discipline,there are $50\%$ of the total girls and $40\%$ of the total boys. In the $HR$ discipline,there are $30\%$ of the total girls and $30\%$ of the total boys. In the Finance discipline,there are $20\%$ of the total girls and $30\%$ of the total boys. $7$ boys and $9$ girls are in both $HR$ and Marketing. $6$ boys and $7$ girls are in both $HR$ and Finance. $5$ boys and $8$ girls are in both Marketing and Finance. $2$ boys and $3$ girls are enrolled in all three disciplines. What is the ratio of boys to girls only in the Marketing discipline?