This content was created by Rob Langman. This content was uploaded by Rob Langman. This is a YouTube video titled "How To Calculate Percentages Of Amount" (created 2024-04-15) — a solo instructional lesson by a presenter who introduces mental methods for teaching children to find percentages. The presenter (identifying himself as Ben) explains percent as 'out of 100', demonstrates place-value and bar-model approaches, and works through examples: 10% of 32 kg = 3.2 kg; 5% of 60 cm = 3 cm (half of 10%); and 15% of £610 = £91.50 by partitioning into 10% + 5%. The video emphasizes using multiple methods (bar models, decimals, halving) and teaching tips for primary learners.
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Hi, my name's Ben, and in this video I'm going to show you how to find percentages of amounts using mental methods. Now, before we begin, it's really important when dealing with percentages that children are really clear about the fact that percent, meaning out of 100, and that percentages we always deal with 100. It might be that sometimes they're dealing with questions with 200% or more, but it always comes down to 100% that is really important. Okay, we've looked at place value before, and here's our question. What is 10% of 32 kilograms? So if we write the number 32 in there, so we have the 3 in our tens column and the 2 in our ones column. And we are going to divide by 10. That means that we move one place value column to the right. So the two ones go into the two tenths column, and the three tensions moving to the three ones column, giving us 3.2. So the answer of what is 10% of 32 kilograms? Is 3.2 kilograms. Here's the next question. What is 5% of 60 centimeters? So here we have the bar, and you can see that the 60 centimeters, that's 100%. It's the full amount. And we're breaking the other bar here into 10. And again, the reason why we do that is really important that children understand is that 100 divided by 10 equals 10. And that's how we break the chunks up. So 10% is 1 10th or 0.1, and I would write that in. So this One here is 10%. And if we do 60 divided by 10, we get 6. So 10% of the amount equals 6 centimeters. What is a valuable question here to ask the children is if 10% is 6, what do they then think is 5%? And hopefully they can tell you that 5% is half of 10%, and therefore half of 6 cm will be 3 cm. What is 5% of 60 cm? The answer is 3 cm. And the last question here, you're really starting to stretch the children and you're getting them to apply their understanding of finding 10% and finding 5%. So what is 15% of 610 pounds? Well, we can partition 15 into 10 and 5 and first find 10% by dividing 610 by 10 to give us 61 pounds and then halving the 61 pounds, find 5%, which is £30.50, and then recombining them together to get 15%, which is £91.50. Now, it's really important that when you're teaching this to the children, they can use a variety of methods. Bar models are really helpful, but you can relate it to decimals and percentages too. And also that when they find 10%, which is key, that sometimes actually other methods are quicker. So if we were finding 50% or 25%, that maybe not finding 10% is always faster to find 50, you could just halve that. But that's where you would openly discuss that with the children.
