The ratio of spirit and water in two mixtures of 20 litres and 36 litres is 3 : 7 and 7 : 5 respectively. Both the mixtures are mixed together. Now the ratio of the spirit and water in the new mixture is ?

In 20 litres mixture - 1; sum of ratio = 3 + 7 = 10
10 units = 20 litres
1 unit = 20/10 = 2

In 36 litres mixture - 1; sum of ratio = 5 + 7 = 12
12 units = 36 litres
1 unit = 36/12 = 3

In 20 litres mixture - 1; spirit : water = 3 × 2 : 7 × 2 = 6 : 14
In 36 litres mixture - 2; spirit : water = 7 × 3 : 5 × 3 = 21 : 15

spirit : water = (6 + 21) : (14 + 15) = 27 : 29