If $a: b = 3: 5$ and $b: c = 4: 7,$ then $a: c$ is equal to

$A$ and $B$ have their monthly incomes in the ratio $8: 5,$ while their monthly expenditures are in the ratio $5: 3.$ If they save ₹ $12,000$ and ₹ $10,000$ monthly respectively,then the difference in their monthly incomes is (in ₹): (in $,000$)

If $A : B : C = 2 : 3 : 4,$ then $\frac{A}{B} : \frac{B}{C} : \frac{C}{A}$ is equal to

₹ $1050$ are divided among $A, B$ and $C$ in such a way that the share of $A$ is $\frac{2}{5}$ of the combined share of $B$ and $C$. $A$ will get (in ₹):

$A$ man spends $Rs. 2310$ on an average during the first $8$ months from his income. During the next $4$ months,he spends $Rs. 1800$ on an average from his income,but he had taken a loan of $Rs. 1680$ apart from his income to meet his expenses. If he spent all that he had,what is the ratio of his average income to his average expenditure?

What must be added to each term of the ratio $2:5$ so that it may equal to $5:6$?