About the PSLE problem in the previous post - Thanks to the two participants who attempted the problem. And congratulations to Victor. I didn't work out the sum myself, I looked at the solution and I find it logical.
The solution, below, is given in the blog.
Once upon a time you could get zero for your maths tests because some teachers were lazy and just looked at the answers. There were no marking schemes either. Nowadays there are marking schemes with marks given for knowledge, understanding and application. For example, in a problem sum, if you do not know how to do it and you just write down distance = speed x time. If it is relevant in solving the problem, you might get one consolation mark for knowledge.