A lump of two metals weighing 18 gms is worth Rs.87 but if their weight be interchanged, it would be worth Rs.78.60. If the price of one metal be Rs.6.70 per gm., find the weight of the other metal in the mixture.

Let Wa the weight of metal A and Wb the weight of metal B and X the price of metal B We can write the following system of three equations: Wa + Wb = 18 Wa x 6,70 + Wb x X = 87 Wb x 6,70 + Wa x X = 78,60 Solving this system yields Wa = 10 and Wb = 8

In what ratio must a grocer mix two varieties of tea worth Rs. 60 a kg and Rs. 65 a kg so that by selling the mixture at Rs. 68.20 a kg he may gain 10%?

The age difference between two brothers is 6 years. After 6 years the ratio between the age is 8 : 5. What would be the sum of their present ages?