BrainDen.com - Brain Teasers
• 0

## Question

In a sequence , in general , i.e in most of the cases , we always proceed to find the numbers in ascending order . For a change , let's try it in the descending order. We generally do not attempt to design such a sequence as it has to start from infinity .

So in this sequence , there are no numbers prior to the first number(to reduce the complexity) of the sequence . So just start from the first number .

Find the missing number :

97 81 79 63 61 54 _ 45 43 .....

## Recommended Posts

• 0

52?

##### Share on other sites
• 0
52?

No , sorry . Not the right answer but a good try . Keep trying.

Edited by grey cells

##### Share on other sites
• 0
In a sequence , in general , i.e in most of the cases , we always proceed to find the numbers in ascending order . For a change , let's try it in the descending order. We generally do not attempt to design such a sequence as it has to start from infinity .

So in this sequence , there are no numbers prior to the first number(to reduce the complexity) of the sequence . So just start from the first number .

Find the missing number :

97 81 79 63 61 54 _ 45 43 .....

50.

Something along the lines of the digits add to 5, and 50-5=45.

I see some of that in the sequence, but I don't see all the rules in the sequence.

• 0

47

• 0

43

##### Share on other sites
• 0
43

It can't be that, though, because it's a sequence of numbers in descending order, isn't it?

• 0

47?

##### Share on other sites
• 0
In a sequence , in general , i.e in most of the cases , we always proceed to find the numbers in ascending order . For a change , let's try it in the descending order. We generally do not attempt to design such a sequence as it has to start from infinity .

So in this sequence , there are no numbers prior to the first number(to reduce the complexity) of the sequence . So just start from the first number .

Find the missing number :

97 81 79 63 61 54 _ 45 43 .....

It looks to me like 52 works...,or at least no evidence was given to show that it is incorrect.

The sequence that makes 52 work is the following:

Subtract the sum of the digits from the number, (eg 97-(9+7)=81).

Then subtract 2

and repeat.

Notice that if you pair up the second and third, the fourth and fifth, etc that the difference is always 2.

##### Share on other sites
• 0
It looks to me like 52 works...,or at least no evidence was given to show that it is incorrect.

The sequence that makes 52 work is the following:

Subtract the sum of the digits from the number, (eg 97-(9+7)=81).

Then subtract 2

and repeat.

Notice that if you pair up the second and third, the fourth and fifth, etc that the difference is always 2.

I agree, 52 seems to fit perfectly

• 0

43

##### Share on other sites
• 0
43

43 doesn't work it's in a descending order. Plus please use a spoiler in the future

##### Share on other sites
• 0

OK . Sorry for the delay guys . I got up late this morning(headache).

Yeah . 52 seems to fit the sequence . First Nikyma got it and then Eventhorizon gave the right explanation . And Noct too is right .

But what I had in mind was something different . So I will add a couple of numbers to the sequence to make it clear :

New sequence : 97 , 81 , 79 , 63 , 61 , 54 , _ , 45 , 43 , 36 , 31 .....

OK . This definitely makes the sequence clearer.

##### Share on other sites
• 0

Hey ! This one isn't solved yet . You guys were pretty close . Try solving the sequence , I have added just a couple more numbers to the sequence .

##### Share on other sites
• 0

I tried several fashion...every thing results in 52...but u r saying its not correct

##### Share on other sites
• 0

53...the missing alternative prime!!!

##### Share on other sites
• 0
53...the missing alternative prime!!!

Yes . Storm has got it .

52 would have been correct for the first sequence , i.e. , before I had added a couple more numbers to the sequence .

Sequence : 97 81 79 63 61 54 53 45 43 36 31....

97 -> 9+7=16 .

97-16=81(2nd number in sequence)

The prime number after 81(in descending order) would be 79(3rd number in sequence).

Again 79 -> 7+9=16.

79-16=63(4th number in sequence)

The next prime number would be 61(5th number in sequence).

And so on....

I thought some of you would see 97 and 79 , and go for palindromic sequences . But I think nobody fell for that one.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×