How many kg of rice at Rs.60 per kg, must be mixed with 30 kg of rice at Rs.25 per kg, so that he may on selling the mixture at Rs.50 per kg gain 25% on the outlay? 

Let x kg of rice at Rs.60 per kg,  be mixed with 30 kg of rice at Rs.25 per kg,

So cost price of the mixture= 60x+750

unit sales price= 50 Rs per kg

Total quantity=30+x 

$\left(30+x\right)50=\left(60x+750\right)\frac{125}{100}\Rightarrow x=22.5$