C. 1/5
Feedback Suppose the vessel initially contains 8 litres of liquid.
Let x litres of this liquid be replaced with water.
Quantity of water in new mixture =3 -3x/8+ xlitres
Quantity of syrup in new mixture =5 -5x/8litres
3 -3x/8+ x=5 -5x/8
5x + 24 = 40 - 5x
10x = 16
x =8/5.
So, part of the mixture replaced = 8/5x1/8=1/5.