Your child's method is not wrong.

We can start with what is left and then complete the bar for red roses to show what was sold. Red roses left is represented by 1 unit.

Done it but the teacher marked it wrong?! Answer 240 for 5 units?

Is the work done in green the corrections that's copied from the board? If it is, I suspect that the teacher didn't 'understand' the previous working in which your child worked out for 4 units and then added 1 more unit to get 240 (though could have just worked out 5 units). I suggest that your child clarifies with the teacher :)

190 + 1 unit = 91 + 2 units Each unit is 99 So Amy & Cathy each has 289 Or 1 unit = 190 - 91 = 99 Cathy = 190 + 99 = 298

Working backwards, start with 1 unit for Amy and 2 units for Cathy. Then complete the bars with other given info.

I was almost blinded by the lightbulb that finally went on in my head when I saw ur final model. Good example. Thanks for sharing!

Wow.. Boey Wai Yen... Thanks for the compliment! Great way to start Monday!

could have been much better if it can be done with one or two models without redrawing, bearing in mind that students in exams are hard pressed for time and have not much time to redraw.

Thank you Mike Tan. Your point is indeed valid. However, I need to point out that this video was done with the intent of explaining. Hence the redrawing etc. Of course, with more practice, it can be done in a faster manner. It is also good to note. This is the last question for paper 2. It's intent is a separator. Those students who have the ability to solve this question are usually the A* scorers and if they are, they should not have a problem with time. Nonetheless, thank you for your feedback. Greatly appreciated

I like Weiqiang's video, coz it's really a step-by-step solution. In the end, the final model was the one that counted. With more such questions, the kids would be more confident with such questions. Eventually, they would be able to 'redraw' the first few models mentally, or more quickly as rough models, and come up with the final model as their working model.

Cheers Boey Wai Yen.

Enjoy ur SG50 weekend, Mike Tan & Tan Weiqiang!

Enjoy! It's going to be a great weekend!

Mister Tan has put plenty of effort into his videos, and all credit to him, I am sure many students have benefited from his tutorials. However I would like to mention that the model method is essentially algebra, as both use the same mechanism. The reason why I bring this up is to assure parents that the mathematics that they have learned as students is still relevant today in the context of using models to solve problems in primary school. At the end of the day, the idea is to teach our children analytical skills and problem-solving skills. Methodology is merely the tool.