slt:Yes, will be good if the question can state that the ribbons must be in 1 piece. In real life, who will notice it if the ribbons are jointed in a deco. I won't spend the unnecessary money. That was what I do when wrapping presents too. I will just take some from another piece to tape onto the main piece, leaving the rest for another present.To most adult, it is quite obvious that the logical answer should be 10. There will be some wastage in one roll which is not long enough (less than 110cm) and therefore can not be used. But then, I am not quite sure if majority of the P6 students can see it that way. The student will have to link it to reality in order to get the correct answer. If the question can be worded more clearly (such as all the ribbons must be in one whole piece), it will certainly help to let them understand that wastages may be incurred. I do not think it is the intention of the question against that.
I am not against linking the concept learned to reality. I do think it is important to be able to do that eventually.
Most of the time, setter set questions in the eyes and thoughts of adults. They do not bring themselves down to the students level and understand how questions can be interpreted by 11-12 yr old kids. Very obvious especially for Science.