**Hi everyone. I'd need some help editing Stack questions.**

**There are some details:**

The variables in the problematic question are:

ww: rand([1,2,3,4,5,6,7,8,9,10,11,12,13,14]);

mm: rand([220,330,440,550,770]);

mv: rand([55,75,170,240,250,310]);

exp: ((mP*wP)/(mP+mR));

ta1: remainder(exp,x);

prem: (ww/100);

form: decimalplaces(((mm*prem)/(mm+mv)),2);

The student is supposed to calculate the mass fraction of HNO_{3} solution of {@ww@} % with a mass of {@mm@} g diluted with {@mv@} g of water, and type in the formula used to calculate the mass fraction, using the following symbols mP, wP, mR.

The inputs are:

ans1 is an algebraic input, the model answer is: decimalplaces(((mm*prem)/(mm+mv)),2)

ans2 is an alg. input as well, and the model answer is: ta1

The response trees:

Potential response tree: prt1 Node 1: Answer test: AlgEquiv; SAns: ans1; TAns: form

Potential response tree: prt2 Node 1: Answer test: AlgEquiv; SAns: ans2; TAns: ta1

So, this is everything the question contains. The problem occurs, when the student enters a decimal number (the correct numerical answer, e.g. 1.6, and the response is:*This answer is invalid. Your answer contains floating point numbers, that are not allowed here. You need to type in numbers as fractions. For example, you should type 1/3 not 0.3333, which is after all only an approximation to one third.*

Any ideas? Thank you in advance.