00:00We're gonna start out easy. You'll have 10 seconds to make number 7 even.
00:19This is not about math, actually. To make 7 even, you only have to take away the letter S at the beginning of the word.
00:28OK, the next one is a bit trickier. Two 4s skipped dinner. How come?
00:48Because they're 8. I mean, 8. Yeah, these are homophones.
00:54The last riddle to warm you up. So what numbers are always on the moon?
01:12Roman numbers. Roman. Sorry, I couldn't resist the pun. On to more serious stuff.
01:20Let's test your logic, shall we? Take a look at this number sequence.
01:31As you see, one digit is missing. Which digit logically follows this series?
01:49If you pick the number 19, congratulations! You see, each time 5 gets added. 4 plus 5 equals 9. 9 plus 5 equals 14. And 14 plus 5 equals 19.
02:09The numbers 6 in between other digits stay the same. They do not change and act more like a frame for all the other digits.
02:19Now take a look at this picture. How many triangles are there? Again, I'm going to help you a bit. So it is 7, 8, 12, 18.
02:31The correct answer is 18. Look, here's how you should count. You have really small triangles on top and bigger ones.
02:53OK, this one is not a riddle, but a quick magic trick to make you the fastest in your class.
03:00If you need to multiply some numbers from 1 to 10 by 9, you don't need anything but your hands.
03:08Place both palms before you and assign each finger a number, just like you can see it on the screen.
03:14If you need to multiply 3 by 9, bend finger number 3. On the right, you still have 7 unbent fingers. That's the first part of the answer.
03:25On the left, only 2. That's the second part. Voila! 9 times 3 equals 27.
03:35Hey, are you a discount hunter? If so, you gotta be quick on counting how much money you're gonna save.
03:41To calculate the discount you're gonna get during a sale without a calculator, use this trick.
03:47For instance, to find out what 5% of 235 is, follow this method.
03:53Step 1. You get 10% of the whole. To do that, just move the decimal point over by one place. 235 becomes 23.5.
04:04Step 2. Keep in mind that 5% is half of 10%.
04:09Divide 23.5 by half. The answer is 11.75. That is also the answer to the original equation.
04:21Alright, this one is just more math magic.
04:25Right, so A% of B equals B% of A. Like 9% of 30 is equal to 30% of 9.
04:36That's it. This trick was really short. I mean, you will probably thank me one day for that when you use it in an exam.
04:45A math trick to save your party. What's bigger? One 18-inch pizza or two 12-inch?
04:52You've got 10 seconds to think.
05:06Well, there are two answers to that.
05:10Geometry claims the area of two 12-inch pizzas is equal to 226 square inches, but the 18-inch pizza is 254 square inches.
05:21Well, from this point of view, you'd rather grab an 18-inch one. But hey, geometry and cooking are two completely different things.
05:29So, it's the weight that matters here. The more the weight is, the more calories there are.
05:33So you know what to choose, and there will be enough pizza for everyone.
05:40Alright, let's have a short pause and have another fun riddle.
05:44So, number 4 wanted to go to a nightclub, but the security didn't let it in. How come?
06:03Because it's two square. I mean, two square. You get the point.
06:09Next one here. This is Triangle Jack, and in the geometry world, everyone says he's rude.
06:16What can rude Jack say to Circle Jerry?
06:20Jerry, you're pointless. Yeah, that doesn't sound quite polite, but it's just geometry. No offense.
06:29Hey, do you know what snake has the most mathematical name?
06:39It's a snake.
06:40Hey, do you know what snake has the most mathematical name?
06:56It's Python.
07:01Back to more serious stuff. Let's assume you need to prove 6 plus 7 equals 1. Can you do that?
07:10Yep, it is indeed correct, but you gotta take a look at that from another perspective.
07:15Let's say these are not numbers, but hours. Do you see what I'm driving at?
07:20Right, 6 a.m. plus 7 hours equals 1 p.m.
07:26Okay, this one is tougher. What if I say 6 a.m. plus 7 hours equals 1 p.m.?
07:31Right, 6 a.m. plus 7 hours equals 1 p.m.
07:37Okay, this one is tougher. What if I say 2 plus 2 equals 5?
07:43Yeah, you may want to advise me on going back to elementary school, but what if I prove it to you? Look here.
07:50Technically, it's wrong, but there are fun methods to prove it otherwise. Here's the simplest method.
07:55Let's assume 0 equals 0. Now, 0 can result from the subtraction of one number with itself.
08:02So let us think that the two figures at the left-hand side and right-hand side are 4 and 10.
08:09So, 4 minus 4 equals 10, minus 10.
08:134 can be written as 2 squared, and 10 can be written as 2 times 5.
08:182 to the power of 2 minus 2 to the power of 2 equals 2 times 5, minus 2 times 5.
08:25And when we twist it a bit, we get 2 minus 2 in brackets, 2 plus 2 in brackets, equals 5, times 2 minus 2 in brackets.
08:35Cancelling 2 minus 2 in brackets from both sides, we get 2 plus 2 equals 5. All proved, right?
08:42Please don't try it out during your math class. I'm sure your teacher won't be impressed. This one is just for fun.
08:50This one's not a math riddle, but yet another magic math trick that may come in handy in an exam.
08:56Here's how you can quickly square a two-digit number that ends in 5.
09:01Let's use the number 35 as an example.
09:04Step 1. Multiply the first digit by itself, plus 1.
09:08Step 2. Put a 25 at the end.
09:1235 squared equals 3 times 3 plus 1 in brackets, and 25.
09:183 times 3 plus 1 in brackets equals 12.
09:2212 and 25 equals 1,225.
09:2735 squared equals 1,225.
09:31Voila! Neat, right?
09:33Here comes another multiplication trick.
09:36To easily multiply any number by 5, simply divide the number by 2 and multiply it by 10.
09:43For example, multiply 64 by 5.
09:47Step 1. Divide 64 by 2 equals 32.
09:51Step 2. Multiply 32 by 10.
09:55All you need to do is add a zero at the end.
09:58You got 320, and you're done!
10:01You got 320, and it only took you 5 seconds!
10:07A bit more magic.
10:09You already know how to multiply by 5 in no time, and you can do the same with multiplying by 6.
10:15Disclaimer. It only works for even numbers.
10:18So, let's see how it works.
10:20Let's say you need to multiply 4 by 6.
10:23First off, you need to divide 4 by 2. You got 2.
10:27Next, place 4 after 2, and you get 24.
10:31That's the final answer!
10:33Yeah, this may not work with bigger numbers.
10:35Seems like it's easier to learn the multiplication table by heart.
10:41Hey, I can read your mind.
10:43If you don't believe me, then think of a number.
10:45Keep it simple. You'll have to do a bit of math here.
10:48And you may probably need a calculator to play this guessing game with me.
10:52So, you think of a number.
10:54Now multiply it by 3.
10:55Done? Okay.
10:57Now add 6.
10:59Next step, you need to divide this number by 3.
11:02Now subtract the number you thought of from the resulting number.
11:06Let me guess. As a result, you got 2, right?
11:10No magic involved.
11:12It's just a smart math riddle. It works with any number.
11:17If you ever struggle to learn all the digits in the pi number, just give up.
11:22There are trillions of them.
11:23But there is a trick to remember at least 7.
11:26Just say, how I wish I could calculate pi.
11:29There are 3 letters in how, 1 in I, 4 in wish, 1 in I again, 5 in could, 9 in calculate, and 2 in pi.
11:41You got 3.141592.
11:48The last but not the least riddle for you.
11:505 people build a barn in 8 hours.
11:53How long will it take 12 people to build a barn?
12:08It won't take any time at all.
12:10Why would they build a new barn if those 5 have already done that?
12:14Give the guys a break.
12:16Plus, this one is not about math at all.
12:18We humans are pretty complicated and we don't obey math that much.
12:22What if these 12 people will split into 2 teams of 6 and start playing volleyball instead of building a barn?
12:48Answer in the comments below.
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