In a zoo,there are rabbits and pigeons. If the heads are counted,there are $200$ and if legs are counted,there are $580$. How many pigeons are there?

$A$ mixture of $30 \ L$ contains milk and water in the ratio of $7:3$. How much water should be added to it so that the ratio of milk and water becomes $3:7$? (in $L$)

$8$ litres of water is added to $32$ litres of a solution containing $20 \%$ of alcohol in water. What is the approximate concentration of alcohol in the solution now? (in $\%$)

How many $Kg$ of tea,worth ₹ $25$ per $Kg$,must be blended with $30 \ Kg$ of tea worth ₹ $30$ per $Kg$,so that by selling the blended variety at ₹ $30$ per $Kg$ there should be a gain of $10 \%$?

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 $kg$.

$300$ $gm$ of sugar solution contains $40 \%$ sugar. How much sugar (in $gm$) should be added to make the concentration $50 \%$ in the solution?