**Hello everyone.**

**I'd like to ask you for some help with the Stack question type. I must confess, and you'll see that, I'm a complete novice in Moodle questions, so I'm sorry if there're some mistakes in the syntax or whatever... I've created a very simple question chemistry based, it is in my language (Slovak), so I'll try to translate it into something that will make sense. So, the question itself looks like:**

**Calculate the mass of KCl that is required to get a solution with a mass fraction of {@ww@}% KCl as the mass of the solution is equal to {@mm@} g.**

**When submitting the formula using which you calculated the mass of KCl, type in wA as the mass fraction of KCl, and mR as the mass of the whole solution, include all steps.**

**1.) Mass of KCl: \(m (KCl)\) = input:ans1 validation:ans1 g**

**2.) Formula you used to calculate the mass of KCl: \(m (KCl)\)= input:ans2 validation:ans2**

^{}

**The valuables are the following: **

ww: rand([2,3,5,7,11,13,17,19]);

mm: rand([200,300,500,700,1100,1300,1700,2000]);

exp: (wA/100)*mR;

ta1: remainder(exp,x);

**The general feedback part includes the following info:**

### SOLUTION

w KCl = {@ww@} %

w (KCl-nondimensional) = {@ww@}/100

m (of the solution) = {@mm@} g

#### Calculation

m(KCl) = {@ta1@} g

m(KCl) = ({@ww@}/100)*{@mm@} g

m(KCl) = XXX

Now, if everything's clear, I can proceed to my question itself. Instead of the three Xs I'd like to have there the right numerical answer

coming out of the right formula), so the mass of KCl needed for the solution's preparation.

Thank you in advance. Please, if you can't help, suggest a forum or another page that could lend me a hand solving this.

In case you need other information to understand what I mean, please, do look up this:

1.) inputs

Input:ans1

requires an algebraic input (number) and the formula (model answer) = (ww/100)*mm

Input:ans2

requires an algebraic input (the formula, which is (wA/100)*mR), the model answer is ta1

2.) response trees

Potential response tree: prt1

**Node 1: Answer test AlgEquiv ; SAns ans1 ; TAns (ww/100)*mm ; the other parts remain unchanged**

Potential response tree: prt1

Node 1: Answer test AlgEquiv ; SAns ans2 ; TAns ta1 ; the other parts remain unchanged