At my sister's suggestion, i decided to let N try simple problem sums. I thought it was a good way to check if N could read and understand the problem. I first wrote the above problem, before i could even write 'how many altogether?', the boy gave the answer '4!'.
Also to check if he would know if the problem requires him to add or subtract, i wrote a subtraction sum for him. No sweat- he could tell me '50-3'. I guess it was the phrase 'take away' that helped (he knows take away means to subtract).
Just for fun, i wrote a slightly complicated sum- see above. At first, he added all of the red & blue cars. But i made him read again and told him to add only the red cars. We practice a couple of times and he understood it thereafter.