Showed my son a simple method for calculating percentages, he was surprised that they were not told about it at school
This year my youngest son finished the 5th grade and once again became an excellent student. He's a very smart guy, but a lot can be forgotten during the holidays. Therefore, every summer, in order to consolidate the knowledge that he received at school, we repeat all the material in the main subjects with him (I do mathematics with him, and my wife speaks Russian and literature). During the holidays, we try not to overload the child and conduct 2-3 lessons per week (this is quite enough so as not to forget the passed material).
Last week my son and I repeated a simple topic related to calculating percentages, which he can handle with ease. I'm sure you all remember how to find the percentage of some number (for example, 60% out of 80).
Everything is simple here and we were all taught to do it in the following way. At the beginning we wrote down that the number 80 is 100%.
And then, we made the proportion that 80 is related to X (unknown number) as well as 100% is related to 60%. As a result, we got this geometric proportion.
Next, we just multiply 80 by 60 and divide by 100. We do some simple math and get the answer 48.
Yes, everything is simple here, but to solve this problem it is necessary to make quite a lot of notes, so I showed my son another simple method of calculating percentages and he was very surprised that they were not told about this at school (by the way, in my school years, they also did not talk about this method and I learned about it from my grandfather).
For example, let's find which number is 40% out of 70.
This time we will not use proportion and will solve everything much easier. And so, all we need to do is pay attention to the first numbers (underlined with a red line).
We write down the numbers 4 and 7 below and put the multiply sign between them.
That's all, it remains to count and the answer will be 28. You can check the answer by solving the example using proportion. Well, how do you like this way of calculating percentages? I'm sure not everyone knew about him!