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Answer:
31.5 kilograms of a 5% salt solution and 13.5 kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution .
Step-by-step explanation:
Let us assume that the number of kilograms of a 5% salt solution used be x .
Let us assume that the number of kilograms of a 15% salt solution used be y .
As given
A 5% salt solution and 15% salt solution must be mixed together to make 45kg of an 8% salt solution .
Equation becomes
x + y = 45
5% is written in the decimal form .
= 0.05
15% is written in the decimal form .
= 0.15
8% is written in the decimal form .
= 0.08
Thus
Concentration of 5% salt solution × Number of kilograms of 5% salt solution used + Concentration of 15% salt solution × Number of kilograms of 15% solution used = Concentration of 8% salt solution × Number of kilograms of 8% salt solution
Thus
0.05x + 0.15y = 0.08 × 45
Simplify the above
5x + 15y = 360
Thus two equations becomes
x + y = 45
5x + 15y = 360
Multiply x + y = 45 by 5 and subtracted from 5x + 15y = 360 .
5x - 5x + 15y - 5y = 360 - 225
10y = 135
y = 13.5 kilograms
Put value of y in the equation
x + 13.5 = 45
x = 45 - 13.5
x = 31.5 kilograms
Therefore the 31.5 kilograms of a 5% salt solution and 13.5 kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution .