Find Amount of Salt

[harpazo]

John has 20 ounces of a 20% of salt solution. How much salt should he add to make it a 25% solution?

Solution

Let s = amount of salt John should add to make a 25% solution

20(0.20) + s = 0.25(20 + s)

Correct set up?

 

[Dr.Peterson]

Yes. But you should really specify the unit (ounces) in the definition.

A good way to convince yourself (and us) that your equation is right is to explain in words what each side means: the amount of salt in the solution, plus the added salt, equals the amount of salt in the desired solution.

 

[harpazo]

Yes. But you should really specify the unit (ounces) in the definition.

A good way to convince yourself (and us) that your equation is right is to explain in words what each side means: the amount of salt in the solution, plus the added salt, equals the amount of salt in the desired solution.

My main focus is setting up the right equation.

 

[Dr.Peterson]

My main focus is setting up the right equation.

And, as we've seen in the time problem, the definition of variables is an essential part of "setting up the right equation" (and then interpreting the result).

 

[harpazo]

And, as we've seen in the time problem, the definition of variables is an essential part of "setting up the right equation" (and then interpreting the result).

Yes, you're right.