How many kg of tea worth Rs 25 per kg must be blended with 30 kg of tea worth Rs 30 per kg so that by selling the blended variety at Rs 30 per kg there should be a gain of 10%?

Cost price of the mixture $$\times$$ (100 + Gain)% = Selling price of the mixture

Cost price of the mixture $$\times$$ (100 + 10)% = 30

Cost price of the mixture $$\times$$ 110% = 30

Cost price of the mixture = $$\frac{30}{1.10}$$ = Rs. 27.27

By the rule of mixture and Alligation,

 Let the quantity of tea = x

Type A                                                     Type B

x                                                                        30

25                                                                      30

                                27.27

2.73                                                                    2.27

$$\frac{x}{2.73}$$ = $$\frac{30}{2.27}$$

x = $$\frac{30\times2.73}{2.27}=36 kg$$