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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?
• There was something on the side that said the "Sal meant to say 88 but accidently said 89."
• Can a pattern alternate? ie. Add three, then subtract five, then add three again, then subtract five, etc.
• Yes
for example -
1,2,5,6,9 (+1+3+1+3)
• I don’t get it it doesn’t make sense pls someone help )=
• it it like you add number that is like times
(1 vote)
• It doesn’t make sense
• It dosn't really make sence to me, sorry. )= :(.
• Can you times 9?
(1 vote)
• 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 :)
• It does not make sense! 67+21=88!
• That's a well-known error in the video, so ignore that bit.
(1 vote)
• sal 61 and 21 equals to 88 not 89
• 82 Not 88
• 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)