P is \(1\frac{3 }{7}\) times as heavy as water and water is \(1\frac{2 }{5}\) times as heavy as Q. The amount of P that must be added to 7 liters of Q so that the mixture may weigh as much as an equal volume of water will be?

\(4\frac{2 }{3}\)

\(1\frac{3 }{7}\) = \(\frac{10}{7}\)

\(1\frac{2}{5}\) = \(\frac{7}{5}\)

Ratio of weight :

P   :  W  = 10  :   7

W  :  Q  =  7  :   5

Hence, P : W : Q = 10 : 7 : 5

Now, ATQ