Mental Addition Trick - Add faster than a calculator in your head! - Free Educational videos for Students in K-12

Mental Addition Trick - Add faster than a calculator in your head! - By tecmath

Transcript


00:0-1	Good day and welcome to the Tech mouth channel .
00:02	What we're going to be having a look at in
00:03	this video is going to be looking at how to
00:05	add numbers together mentally . Okay , so we're gonna
00:07	start out fairly simple and get harder and harder to
00:10	go . So let's launch into an example here .
00:13	So Can you add this in five seconds ? Okay
00:20	. Time's up . Hopefully you've got the answer of
00:23	38 . Okay . Ed , if you did ,
00:26	congratulations . If not , I'm going to show you
00:29	a few techniques on how you can organise these numbers
00:32	quickly in your head so you can add them together
00:35	. Okay . So we'll get back to this particular
00:37	problem at the end and we'll see how you go
00:40	. Okay . You might be able to cheat a
00:42	little bit , remember that answer . But let's ,
00:44	uh , let's get into some how you might actually
00:47	do these in the future . So the biggest trick
00:50	when you're adding these sorts of numbers is first off
00:53	. This is a big trick for mentally adding numbers
00:55	, is to look for compliments . This is the
00:57	first trick . And what do I mean by this
01:00	? These are numbers as follows . So we occasionally
01:02	going to be looking for numbers Like this . I
01:05	say we have a one we might look for its
01:07	complement which is the # nine . We have the
01:10	number to the complementary to is a complement to three
01:15	. Is seven . Now , what you might notice
01:17	with these is that they complement the numbers that add
01:20	up to 10 ? Okay , one plus nine is
01:22	10 or two plus eight is 10 or three plus
01:25	seven is 10 . Maybe we're going to have four
01:27	and six uh and five and five . Okay .
01:31	Or vice versa ? The compliment to nine is one
01:34	of the compliment ages two . So this is a
01:36	two way street sort of thing . So we're gonna
01:38	be looking for compliments . And that's our first trick
01:41	when mentally adding numbers together . So I'll give you
01:44	an example here . So we had I wanted to
01:47	add four , right ? And to not want to
01:52	add these together , we'll start out fairly small .
01:55	What you might notice is we have a set of
01:58	compliments here , we have Okay we have eight and
02:01	2 , So we can add this together straight away
02:04	and we get 10 plus four , it's 14 .
02:10	Okay , we're gonna start out fairly simple with these
02:12	. Okay ? Uh And you might start out and
02:14	go yeah just add four and eight and get 12
02:16	plus two is 14 . But this is going to
02:18	be moving towards trying to get this much bigger strings
02:22	and numbers . So I'm gonna go through first trying
02:25	to recognize these compliments very rapidly and then adding these
02:28	together . Okay so what about we give you ?
02:32	I'll give you another example . What about if you
02:35	were to trying to add uh three nine and 7
02:42	together . Okay so first notice the compliments . Okay
02:48	which are those ? Well these are three and seven
02:52	. Okay these are compliments of each other so they're
02:54	straight away 10 plus nine is 19 . You see
02:59	how easy that is . Okay we are going to
03:02	get the biggest strings and numbers . Okay so so
03:05	let's let's get up to actually a bigger string right
03:07	now . What about we do 239 and five and
03:11	I want to add these together . So what's the
03:13	compliments that we have here ? Well you might notice
03:16	that there's no set complements that we see but you
03:19	might notice that two plus three is five Plus another
03:22	five is 10 . Okay so it's almost like these
03:26	guys can be added together to make compliments as well
03:29	and so look out for this sort of thing .
03:31	Okay , so two plus three is five plus five
03:34	is 10 plus nine is 19 . Okay . What
03:41	about I'll give you a different example . What about
03:45	we do ? Nine plus five plus seven plus one
03:52	. Okay . With the compliments here We have nine
03:56	and one is confluence . Okay , so they're 10
03:59	And then we just add these as we go to
04:01	10 , 15 , 22 . You're going to notice
04:07	you still do need to be able to add things
04:08	. There's no little trick of subtracting or taking things
04:11	. Why you still need to be able to add
04:13	fairly quickly ? And so that's a really , really
04:17	good school to be able to have . It's just
04:19	, this is a way of organizing numbers . What
04:21	about we go to a string of five numbers .
04:23	What about we say ? I get you to add
04:25	eight for six plus one plus five plus three .
04:31	Okay so the compliments here we have we have six
04:37	, one and 3 . Okay they're going to add
04:39	up to 10 . It's a 10 plus I'd exciting
04:45	. That's five . He's 23 . Okay . What
04:50	about even biggest string of numbers ? Okay . Um
04:56	I have to rub these out of these strings .
04:57	Going to get so big . What about we start
04:59	to add uh seven plus four plus six plus three
05:05	plus one plus five . Okay what string what can
05:10	we do ? Here we go . seven and 3
05:12	are a complement . We have four and six of
05:14	the compliments . So we have 20 plus one plus
05:18	5 . 21 . 26 . Okay so straight away
05:25	try to recognize these compliments . You see that ?
05:28	Okay what about I'll give you another string of numbers
05:32	here and try not to start adding them until I
05:35	finish writing them all down to see how you go
05:37	with this . Okay so what about we do ?
05:39	Nine plus seven plus four plus three plus one plus
05:45	four plus . Right okay let's start trying to add
05:49	these . So we have compliments nine and one .
05:52	We have seven and three . Okay so that's 20
05:55	24 . 28 . 36 . Okay . It's a
06:04	lot faster way of doing it , isn't it ?
06:06	Okay . Well I'll tell you what what about we
06:08	go up to In fact what about we just before
06:14	we do that let's go to something . Let's let's
06:15	get a really big string . Let's get a string
06:17	of 10 numbers . Okay . Okay so just wait
06:21	wait for these until you try to add them .
06:23	So that's 21 plus seven plus six plus five plus
06:27	four plus three plus two plus nine plus six plus
06:33	five plus eight . Look at 123456789 10 11 .
06:39	Numbers have gone a bit overboard there . Okay ,
06:41	let's try to add these . So we have the
06:43	compliments here . We have one 2345 . Okay ,
06:51	so that's 50 Plus six is 56 . How did
06:56	you go with that ? Did you get that really
06:58	quickly ? So I'm going to see how quickly you
07:01	can add these together . Okay , so it's a
07:04	really , really handy technique , isn't it ? Okay
07:07	. What about we go back to the numbers that
07:09	we had at the start . You'll see those negatively
07:11	. Really easy . I reckon there so we'll see
07:15	how you're going these . Okay , the first ones
07:20	we did with these . So can you add these
07:22	together ? Okay , so what do we have ?
07:24	We have 10 , Yeah , 20 30 38 .
07:31	You see how fast it is So I'm not even
07:35	going this place , this is 10 . I'm just
07:37	marking the compliments as I go . Okay . 10
07:39	2030 38 . Okay . Really easy , isn't it
07:43	? Okay , so hopefully you get this idea compliments
07:47	are a great way of adding single digit numbers together
07:50	. And they're also not a bad way of adding
07:51	multiple digit numbers together . We're gonna have a look
07:54	at those in the next video . Okay , so
07:56	anyway , I hope to see you then . Okay
07:58	boy .

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Mental Addition Trick - Add faster than a calculator in your head! is a free educational video by tecmath.

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