Problem sum is always a problem to most children (pun intended).
Well before we even talk about problem sum, the child needs to have a strong foundation in what is called mechanical calculation questions. These are simply questions which deals with straight forward calculation. These are what I would call simple mini problems.
Then we go to what used to be called story sums or now known as problem sums.
Problem sums have it’s own funny mathematical language. A child needs to be able to decode the language. IN most cases, the language is simple for everyone to understand but in some cases it is tricky. Once the child is able to decode the language, they would then have decoded the question.
A mathematician named George Polya came about with the Polya approached to problem solving. If you google George Polya, you will be able to read what he says.
To teach problem sums, we need to take small steps first.
What I would do would be to start with simple problems which are straight forward. Once the child is able to solve this, here is where it differs, I will make the child write out her own questions based on that sum or concept. This would allow the child to understand the way how a question is being asked and allow them to explore how else that question can be asked.
Next, once they are comfortable with these simple problem sums, I will then exposed them to the mid-difficulty problems. Here is where I will try to equip the child with the various different heuristic approaches. In this case, the approaches are like model method, using a table, guess and check, act it out and etc.
This would help the child to gain confidence in using these heuristic approaches.
Finally, when they are comfortable with the mid difficulty questions, then I will move them to the difficult ones, knowing that the child has the confidence for easy and mid-difficulty.
The important thing to take note is that, we should let the child develop their skill step by step. Sad to say the duration may be slower than what we may like but the reward would be greater.
The common mistake is to jump to the difficult questions and if the child could not do it, we would simply kill their interest and create a fear for math in them.