Interpreting Functions linear functions Linear, Quadratic, and Exponential Models* Solving Linear Equations

Solving for a variable


Why do kids make this mistake?

4 replies on “Solving for a variable”

They actually did twice the work required…they ‘solved’ for Y and gave you the X to go with it too! 😉

I think the brain tends to skip the ‘wordy’ instructions and go straight to the ‘math’. It sees the equation and can immediately see one solution. If the equation was 2x + 3y = 1, that thought process might have been interrupted and they might have thought about it more.

But maybe they should get a little credit for finding one solution to the problem. 🙂

When I had the same kind of answers from students, I asked them why they constantly want to say the variable’s value is 1. They told me when they just started learning about variables, the teacher told them, “If there is no number (coefficient) with the variable, it’s one.” To me this statement makes it sound like the variable is 1, not the coefficient. Maybe they just see a variable, plug in 1, and that’s it?

Um, I think the issue is the wording of the question. “Solve for y” v. “Solve for y in terms of x.” If you wanted the latter, you didn’t ask that. If you actually wanted them to give A solution for the equation, then they did (x = 1; y = 1 works), but then, you didn’t ask that either.

Unless I’m missing something trivially obvious, the question as stated leaves something to be desired.

I think that this student made this mistake because he or she saw this problem as 2(1) + 3(1) = 5, which is correct. But not in terms of solving for y in terms of x. The student is not familiar with problems solving for y in terms of x or vise versa. The student just went straight to the number problem and skipped the part that said “solve for y”. It also seems like students who make this mistake are not comfortable with these problems because they might of read “solve for y” but did not understand what that meant.

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