Ratio and Proportion :
1. In a school, 30% of the boys are same in the number as 1/2 of the girls. What’s the ratio of boys and girls in that school?
Solution:
(30/100)B = (1/2)G
B/G = 100/60 = 5/3
The required ratio is 5:3
2. Three containers have their volumes in the ratio 1:2:5. They are full of mixtures of milk and water. The mixtures contain milk and water in the ratio of (1:3), (2:1) and (3:1) respectively. The contents of all these three containers are poured into a fourth container. The ratio of milk and water in the fourth container is:
Solution:
Let their volumes be x, 2x and 5x respectively.
Milk in the 3 containers = x(1/4) + 2x(2/3) +5x(3/4)
= x/4 + 4x/3 + 15x/4
= 64x /12.
Water in the 3 containers = x(3/4) +2x(1/3) + 5x(1/4)
= 3x/4 + 2x/3 + 5x/4
= 32x/12.
The required ratio = 64x/12 : 32x/12
= 2:1
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