A short instructional video (presenter Ben) demonstrating how to use bar models to solve a multi-step addition/subtraction word problem. The worked example: Jane has 232 cakes, bakes 197 more (total 429), Mohammed needs 500 for a party, so Jane must bake 500 − 429 = 71 more. Emphasises understanding the question, underlining key facts, drawing roughly proportional bar-model parts, and using number lines or subtraction to find the missing part.
Chapters
Hi, my name is Ben and in this video we're going to be looking at how to solve multi step word problems with addition using the bar model. Here is our. Jane has 232 cakes in her bakery overnight. She baked 197 more cakes. Mohammed wants to buy 500 cakes for his party. How many more cakes does Jane need to bake? The most important thing that you do here is make sure that the children really understand this question, that they go through it, they underline the key information and they understand what operations they've got to go through. Then we can use the bar model to try and represent this. Here we have the 232 cakes that she's already got in her bakery. Then we can add on the other 197 that she baked overnight. It's important here with each part of the bar model that it's roughly proportional, but it doesn't matter if it's not exact. Then we can see that the part become a whole of 429. And we need to figure out, let's go back to the question, how many more cakes does she need to bake for Mohammed? She needs to make 500. So here we can put the total cakes that she needs to bake, which is 500. What is a good idea for the children here is to look at this bar and maybe even make it shorter and then they can identify whether that's accurate or not. That's a really good way to elicit understanding. So from this part we've got the part part to make 429, we've got the whole of 500 which we need to get to. So we need to know and we need to calculate what that missing part is to make it equal. And there the children can use a variety of methods. They can use a number line or they can do 500 minus 429. Number line is probably the best. And then they can realise that they get the answer of 71. And that's the answer. Jane needs to bake 71 more cakes to make her total of 500. And that is one way of using the bar model to show understanding of word problems.
