Question

How many kilograms of tea at Rs 50 per kg should be mixed with 35 kg of tea costing Rs 60 per kg so as to sell the mixture at Rs 57 per kg without gaining or losing anything in transaction?

Answer 1

Let x Kg of Rs.50 per kg tea should be added with 35 kg of tea costing Rs.`(60)/"kg"`.
Total weight of tea after mixing = (x + 35) g
Selling price of (x + 35)Kg = (x + 35)57Rs.
But here S.P. = C.P.
C.P. of the tea 
= Rs.(50x + 35 x 60)
⇒ (x + 35)57 = 50x + 2100
⇒ 57x + 1995 = 50x + 2100
⇒ 7x = 105
⇒ x = 15kg
Therefore, 15 kg of Rs.50 per kg should be added.