Question

In what ratio must a mixture of 15% spirit strength be mixed with that of 25% spirit strength to get a mixture of 21% spirit strength? Options: 1) 1 : 3 2) 2 : 3 3) 3 : 4 4) 4 : 5 correct answer: 2 : 3

Answer 1

Answer:

let the ratio be x:y

that is x litre of 15% and y litre of 25%  are mixed    but  we get 21%

so  [ 15x +25y ]/[x+y] =21

15x +25 y=21 x+21 y

25y -21y =21x -15x

4y = 6x

2y =3x

2/3=x/y

the ratio x:y = 2:3