Allegation is a method to find the ratio in which two or more indignant are mixed to produce a mixture or solution.
The equation represents the total liters of acid that are needed is,
![0.5x+0.9y=6](https://tex.z-dn.net/?f=0.5x%2B0.9y%3D6)
Thus the option 3 is the correct option.
<h3>What is allegation?</h3>
Allegation is a method to find the ratio in which two or more indignant are mixed to produce a mixture or solution.
Given information-
A scientist needs 10 L of a solution that is 60% acid.
The percentage of two acid solution are 50% and 90%.
Variable<em> x</em><em> </em>represent the number of liters of the 50% solution.
Variable<em> y </em>represent the number of liters of the 90% solution.
Quantity of acid from 50% solution is
liters, and quantity of acid from 90% solution is
liters.
As the scientist needs 10 L of a solution that is 60% acid. Therefore the quantity of acid in 60 percent acid solution is,
![a=10\times\dfrac{60}{100} \\a=6](https://tex.z-dn.net/?f=a%3D10%5Ctimes%5Cdfrac%7B60%7D%7B100%7D%20%5C%5Ca%3D6)
Thus 6 liters of acid required by the scientist. As to get the 6 liters of acid from 50% and 90 percent solution, we need to add the amount of acid in these solutions.Thus,
![0.5x+0.9y=6](https://tex.z-dn.net/?f=0.5x%2B0.9y%3D6)
This is the required equation.
Hence the equation represents the total liters of acid that are needed is,
![0.5x+0.9y=6](https://tex.z-dn.net/?f=0.5x%2B0.9y%3D6)
Thus the option 3 is the correct option.
Learn more about the mixture and allegation here;
brainly.com/question/24372098