VeritasPrepKarishma wrote:

aselfmademan wrote:

A certain drink of type A is prepared by mixing 4 parts milk with 3 parts fruit juice. Another drink of type B is prepared by mixing 4 parts of fruit juice and 3 parts of milk. How many liters of fruit juice must be added to 14 liters of drink A to convert it to drink B ?

a) 4

b) 2/3

c) 3.5

d) 3

e) None of these

Simply use the weighted average concept:

w1/w2 = (A2 - Aavg)/(Aavg - A1)

Amount of fruit juice/Amount of type A drink = (4/7 - 3/7)/(3/7 - 0) = 1/3

Amount of fruit juice/14 = 1/3

Amount of fruit juice added = 4.67 lts

For more on weighted averages, mixtures and details of this method, check out:

http://www.veritasprep.com/blog/2011/03 ... -averages/http://www.veritasprep.com/blog/2011/04 ... -mixtures/Karishma I approached this as follows :

Drink A-> Milk -4 parts; fruit juice-> 3 parts => concentration of milk = 4*100/7

Drink B-> Milk - 3parts; fruit juice-> 4 parts => concentration of milk = 3*100/7

(I am considering concentration of milk as that is the constant in both cases, concentration of fruit juice varies)

I just applied this to the formula ->

initial conc*initial vol. = final conc*final vol => 4*100*14/7=3*100* final vol/7

therefore final vol = 56/3

Amount of fruit juice added = final volume - initial vol = 56/3-14 = 4.67

Is this correct?

Thank you for your help.