Let the total volume of vessel = ‘x’ litres Initially, the % of spirit in the mixture = 18% After the replacement of 8 litres of mixture with water, its % = 15% 0.18x – 8 ×
18
100
= 0.15 x 0.03x = 1.44 x = 48 litres Alternative: Apply the rule of alligation,
W
S
=
18−15
15−0
=
3
15
=
1
5
Water is 8 litres, so spirit is 40 litres and total mixture is 48 litres.