ratio proportion

[mitaliisrani]

A milkman takes one part of a milk water mixture of 80% concentration and three parts of a milk water mixture of 40% concentration and takes 60litres of the new mixture. How much water should evapourate from 60 litres of the mixture to make it of 60% concentration?

A) 25
B) 10
C) 20
D) 15
E) 35

OA: B
Plz help solve with explnations

[clock60]

(0,8*15+0,4*45)/(60-x)=0,6
x=10

[mitaliisrani]

(0,8*15+0,4*45)/(60-x)=0,6
x=10

can you plz explain the logic thnx!

[kvcpk]

A milkman takes one part of a milk water mixture of 80% concentration and three parts of a milk water mixture of 40% concentration and takes 60litres of the new mixture. How much water should evapourate from 60 litres of the mixture to make it of 60% concentration?

type1: milk water mixture of 80% concentration. Which means 80% milk and 20% water.
one part of it is taken.

type 2: a milk water mixture of 40% concentration . means 40% milk and 60% water.
3 parts of this is taken.

60 litres of new mixture is made out of it.
which will have 15 litres of Type1 mixture and 45 litres of type2 mixture.
15 litres of type1 will have 12 litres of milk (because 80% concentration)
45 litres of type2 will have 18 litres of milk (because 40% concentration)

Hence the mixture has 30 litres of milk out of the total 60 litres.
Assume there will be x litres of mixture when some water evaporates.
60% of x = 30
0.6x = 30
x = 50

Hence the mixture should now become 50 litres.

Water amount that needs to evaporate = 60-50 = 10 litres.

Hope this helps!!