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### Course: Class 6 (Foundation) > Unit 5

Lesson 3: Even and odd numbers# Finding patterns in numbers

This video discusses how to identify patterns in number sequences. By analyzing three different sequences, the speaker demonstrates that patterns can involve adding a certain amount to each number, or multiplying each number by a certain amount. It's important to ensure the pattern remains consistent throughout the sequence.

## Want to join the conversation?

- In the 1st pattern isn't 67 + 21= 88 ?

Why is the next number 89 in the pattern?(34 votes)- There was something on the side that said the "Sal meant to say 88 but accidently said 89."(6 votes)

- Can a pattern alternate? ie. Add three, then subtract five, then add three again, then subtract five, etc.(17 votes)
- Yes

for example -

1,2,5,6,9 (+1+3+1+3)(8 votes)

- I don’t get it it doesn’t make sense pls someone help )=(3 votes)
- it it like you add number that is like times(1 vote)

- It doesn’t make sense(2 votes)
- It dosn't really make sence to me, sorry. )= :(.(2 votes)
- I don't think Sal has a video about multiplying by
`9`

yet, but, for now, I'll give some pointers for it!

The**9****times tables**are unique.

The**first****10****multiples**of`9`

are:`9, 18, 27, 36, 45, 54, 63, 72, 81, 90...`

Notice how by going up the tables, the value of the**tens**digit goes**up**by`1`

(increments), and the value of the**ones**digit goes**down**by`1`

(decrements).

This is because`+9`

is the same as`+10`

then`-1`

, or`+(10-1)`

.

This reveals to us a nice**multiplication method**for`*9`

:

Split up`*9`

into`*(10-1)`

and do`*10`

-`*1`

.

For example,`9*5 = (10-1)*5 = 10*5 - 1*5 = 50 - 5 = 45`

.

You can do it with any example, even big ones.`34 * 9 = 34*10 - 34*1 = 340 - 34 = 306`

Hope this helped :)(3 votes)

- It does not make sense! 67+21=88!(2 votes)
- That's a well-known error in the video, so ignore that bit.(1 vote)

- sal 61 and 21 equals to 88 not 89(2 votes)
- Can we not divide in a pattern?(1 vote)
- Dividing in a pattern is basically negative exponents. While 2^2 is 2*2. 2^-2 is (1)/(2^2). If you have any more questions about this, feel free to ask. :)(1 vote)

- 4，25，46,67+ 21=88

does not make sense.(1 vote)- Well, let us format this another way! Into a horizontal addition format.

67

+ 21

————

Now, following the rules of addition, we have to add the ones digits first. Evaluating the sum of 7 + 1, gives us the answer or sum of 8. Let's input that in!

67

+ 21

————

8

Now that we have done that, we have to add the tens place next. Evaluating the expression of 6 + 2 gives us the sum of 8. Let's also input that in!

67

+ 21

————

88

Now, we have no hundreds place, so this is our final and concrete answer. The expression 67 + 21 is equal to 88.

Hope this helps!(1 vote)

## Video transcript

- [Voiceover] What I want to in this video is get some practice figuring
out patterns and numbers. In particular, patterns that take us from one number to a next number in a sequence. So over here, in this magenta color, I go from 4 to 25 to 46 to 67. So what's the pattern here? How did I get from 4 to 25 and can I get the same way from 25 to 46 and 46 to 67, and I could just
keep going on and on and on? Well there's a couple of
ways to think about it. When I see 4 and 25, let's see, 25 isn't an obvious multiple of 4. Another way to go from
4 to 25, I could add 21. Let's see, if I add 21, 4 plus 21 is 25. If I were to go from 25 to 46, well I could just add 21 again. It looks like to go from
one number to the next I'm just adding. I wrote 12 by accident, 21. I'm just adding 21 over and over again. That's going to be 46 plus 21 is 67. And if I were to keep going, if I add 21 I'm going to get to 89. If I add 21 to that I'm going to get 110, and I could keep going
and going and going. I could just keep adding
21 over and over again. The pattern here is I'm adding 21. Now what about over here, in green? When I look at it at first,
it's tempting to say, 3 plus 3 is 6. But then I'm not adding 3 anymore to get from 6 to 12, I'm adding 6. And then to get from 12 to 24, I'm not adding 6 anymore, I added 12. So every time I'm adding twice as much. But maybe an easier pattern might be, another way to go from 3 to 6, isn't to add 3, but to multiply it by 2. So I multiply by 2 to go from 3 to 6, and if I multiply by 2
again, I go from 6 to 12. 6 times 2 is 12. If I multiply by 2 again, I'll go to 24. 2 times 12 is 24 and I could
keep going on and on and on. 2 times 24 is 48, 96, I
could go on and on and on. The pattern here, it's
not adding a fixed amount, it's multiplying each
number by a certain amount, by 2 in this case, to get the next number. So 3 times 2 is 6, 6 times
2 is 12, 12 times 2 is 24. Alright, now let's look at this last one. The first two terms here
are the same, 3 and 6. The first two numbers here. I could say, maybe this is times 2, but then to go from 6 to 9,
I'm not multiplying by 2. But maybe I am just adding 3 here. So 3 to 6, I just added 3. Then 6 to 9, I add 3 again, and then 9 to 12, I add 3 again. So this one actually does look like I'm just adding 3 every time. The whole point here is to see,
is there something I can do, can I do the same something
over and over again to get from one number to the next number in a sequence like this? What you want to make sure
is even if you think you know how to go from the first
number to the second number, you've got to make sure
that that same way works to go from the second
number to the third number, and the third number to the fourth number. But here we figured it out. In this first set of numbers,
we just add 21 every time. This one we multiply by 2 every time. This one we add 3 every time.