Find the ratio in which rice at $Rs. 7.20$ per $kg$ should be mixed with rice at $Rs. 5.70$ per $kg$ to produce a mixture worth $Rs. 6.30$ per $kg$.

Aditya,Sonal,and Nutan contributed $Rs. 50,000$ for a business. Aditya contributed $Rs. 4,000$ more than Sonal,and Sonal contributed $Rs. 5,000$ more than Nutan. Out of a total profit of $Rs. 70,000$,how much did Aditya receive? (in $Rs.$)

In what ratio should wheat at ₹ $32$ per $kg$ be mixed with wheat at ₹ $24$ per $kg$ so that on selling the mixture at ₹ $39$ per $kg$,there is a profit of $30 \%$?

$200$ litres of mixture contains $15 \%$ water and the rest is milk. The amount of milk that must be added so that the resulting mixture contains $87.5 \%$ milk is..........$Litre$

In $50\, g$ alloy of gold and silver,the gold is $80\%$ by weight. How much gold should be mixed to this alloy,so that the weight of gold would become $95\%$? (in $g$)

$A$ sum of $Rs. 6.40$ is made up of $80$ coins which are either $10$-paise or $5$-paise coins. How many $5$-paise coins are there?