00:00We will start with a little math in English. You have 10 seconds to make the number 7 pairs.
00:19It has nothing to do with math in English. To make 7 pairs, you just have to remove the letter S from the word 7.
00:26Well, now we're going to complicate things. 2, 4, we skipped dinner. Why?
00:48Because they are 8 and ate in English is the past of eat.
00:55A last one to finish warming up. Tell me what numbers are still in motion.
01:13Roman numbers. Because in English, roaming means itinerant. Let's get down to business.
01:20Let's test your logic, shall we? Look at this sequence of numbers.
01:254, 6, 9, 6, K14, 6. As you can see, a number is missing. What number logically follows this series?
01:336, 17, 19, 21.
01:49If you have chosen the number 19, congratulations. You see, we add 5 each time. 4 plus 5, 9, 9 plus 5, 14, and 14 plus 5, 19.
02:00The 6 placed between the other numbers do not change. They only somehow frame or separate the numbers of the series.
02:10Now look at this picture. How many triangles are there?
02:15Wait, I'll help you a little. So here are 7, 8, 12, 18.
02:32The correct answer is 18. Look, here's how to count. There are very small triangles at the top and then larger ones.
02:41Well, this is not a riddle, but a little magic trick to make you the fastest in your class.
02:48If you have to multiply a number from 1 to 10 by 9, you need nothing but your hands.
02:54Place your two palms in front of you and assign a number to each finger, as shown on the screen.
02:59If you have to multiply 3 by 9, fold your finger number 3.
03:04On the right, you have 7 unfolded fingers. This is the first part of the answer.
03:09On the left, only 2. This is the second part.
03:12There you go, 9 times 3 equals 27.
03:18So, do you like reductions? If so, you must be quick to calculate how much money you will save.
03:24To calculate the reduction you will get in a store without using a calculator, use this trick.
03:30For example, to find what 5% of 235 represents, follow this method.
03:35Step 1. Find 10% of the total. It's easy, you just have to put a point or a comma before the last number.
03:42235 becomes 23.5.
03:45Step 2. Keep in mind that 5% represents half of 10%.
03:49Divide 23.5 by 2. The result is 11.75. This is also the answer to the original equation.
04:01Very well, now here is another math trick.
04:05So, 1% of B is equal to B% of A. For example, 9% of 30 is equal to 30% of 9.
04:12That's all, this trick was really very short.
04:15You will probably thank me one day when you will have used this trick in a test.
04:20A math trick to save your party.
04:24What is bigger, a pizza of 45.72 cm or two pizzas of 30.48 cm?
04:32You have 10 seconds to think.
04:47There are actually two possible answers.
04:49According to the geometry, the surface of two pizzas of 30.48 cm is equal to 1458.06 cm2,
04:59while that of 45.72 cm is equal to 1638.71 cm2.
05:08So, from this point of view, you would better choose the pizza of 45.72 cm.
05:13But, and, geometry and cooking are two completely different things.
05:18It is the weight that counts here. The higher the weight, the more calories there are.
05:22So you know what to choose, and there will be enough pizza for everyone.
05:28Well, let's take a short break and discover another funny riddle.
05:32Number 4 wanted to go to the nightclub, but the security service did not let him in. Why?
05:49Because he was too square. No luck, friend.
05:57In the world of geometry, everyone says that this triangle, Jack, is impolite.
06:02What could Jack, the impolite triangle, say to Jerry, the circle?
06:19Jerry, you suck. Because it looks like a zero. It's not very polite, but it's just geometry.
06:29Do you know what snake bears the most mathematical name?
06:45The python.
06:49Let's get back to more serious things. Suppose you have to prove that 6 plus 7 is 1. How do you do it?
07:09No, it's not magic. You just have to change perspective.
07:14Let's say that these are not numbers, but hours. Do you see where I'm coming from?
07:19Yes, 6 o'clock in the morning plus 7 equals 1 o'clock in the afternoon.
07:26Well, something more difficult. What if I told you that 2 plus 2 equals 5?
07:31Yes, you will send me back to elementary school, but I can prove it to you. Be careful.
07:37Technically, it is incorrect, but there are funny methods to prove the opposite.
07:43Here is the simplest method. Let's say that 0 equals 0.
07:47Now, 0 can result from the subtraction of a number by itself.
07:51So, let's suppose that the two numbers on the left side and on the right side are 4 and 10.
07:56So, 4 minus 4 equals 10 minus 10.
07:594 can be written as 2 squared, and 10 can be written as 2 multiplied by 5.
08:05By solving the equation further, we get 2 squared minus 2 squared equals 2 times 5 minus 2 times 5.
08:12And when we arrange things a little, we get 2 minus 2, 2 plus 2 equals 5, 2 minus 2.
08:19By canceling 2 minus 2 on both sides, we get 2 plus 2 equals 5.
08:24That's it, it's proven. But don't try this during your math class.
08:28I don't think your teacher will be very impressed. It's just for fun.
08:34This is not a mathematical riddle, but rather another magic trick that can be useful to you during an exam.
08:41Here is how you can quickly calculate the square of a number with two numbers, ending with 5.
08:47Let's use the number 35 as an example.
08:49Step 1. Multiply the first number by itself plus 1.
08:53Step 2. Add a 25 at the end.
08:5535 squared equals 3 multiplied, 3 plus 1, and 25.
08:5912 and 25 equals 1225.
09:0235 squared equals 1225.
09:05Cool, right?
09:08Here is another multiplication trick.
09:11To easily multiply any number by 5, just divide this number by 2 and then multiply it by 10.
09:18For example, let's multiply 64 by 5.
09:20Step 1. Divide 64 by 2 equals 32.
09:24Step 2. Multiply 32 by 10.
09:27Just add a 0 at the end.
09:29You get 320.
09:31And it only took you 5 seconds.
09:35A little more magic.
09:37You already know how to multiply by 5 super easily.
09:40And you can do the same thing with 6.
09:42But be careful, it only works for odd numbers.
09:45So, let's see how it works.
09:48Let's say you have to multiply 4 by 6.
09:50First, you have to divide 4 by 2.
09:52You get 2.
09:54Then, place 4 after 2, and you get 24.
09:57This is the final answer.
09:59This could not work with bigger numbers.
10:02It is better to take the multiplication table by heart.
10:07I can read your mind.
10:09If you don't believe me, think of a number.
10:12Make it simple, because you will have to do some math.
10:15And you will probably need a calculator to play this game with me.
10:19Good. So, you think of a number.
10:22Now, multiply it by 3.
10:24Done? OK.
10:25Now, add 6.
10:27The next step, you have to divide this number by 3.
10:30Now, subtract the number you thought of from the resulting number.
10:34Let me guess.
10:35You got 2 as a result, didn't you?
10:38It's not magic.
10:39It's just a good math trick.
10:41And it works with any number.
10:45If you have ever had trouble learning all the numbers of the pi number,
10:49forget it.
10:50There are billions of them.
10:52But, there is a trick to remember at least 7.
10:56Simply say,
10:58How I wish I could calculate pi.
11:01There are 3 letters in how.
11:031 in i.
11:044 in wish.
11:051 again in i.
11:075 in cooled.
11:089 in calculate.
11:09And 2 in pi.
11:11You get 3.141592.
11:17One last one for the road.
11:195 people build a barn in 8 hours.
11:22How long will it take 12 people to build a barn?
11:39No time at all.
11:40Why would they build a new barn if the first 5 have already done it?
11:44Let people rest a little.
11:46And it has nothing to do with math.
11:48We humans are quite complicated like that.
11:51And we do not obey the math rules.
11:54What if these 12 people formed 2 teams of 6
11:57and started a match instead of building a barn?
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