What value should ‘x’ be in the following sequence?

16 06 68 88 x 98

As ever, please do NOT post your answer, but do feel free to say if you have solved it and how long it took. Also, it is ok to leave fake/joke clues (but no real ones!). Solution on Monday!

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called **PUZZLED** and is available for the **Kindle** (UK here and USA here) and on the **iBookstore** (UK here in the USA here). You can try 101 of the puzzles for free here.

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I like that. It’s a different way of looking at numbers. Very clever. (About a minute.)

Bloomin’ heck. Thats the fastest I’ve ever got one! About 90 seconds. Only downside is I really should be working….

10?

As ever, please do NOT post your answer,

It depends how you look at it.

Thanks, Nick. Your clue helped immensely.

Not bad you just need to know your stuff….

About two minutes. Longer than previous commenters!

I solved it for a min-changing my viewpoint.

Don’t see it.

I’ll return later

still don’t see it!

Can we use letters?

Saw it instantly, but there’s no satisfying answer using numbers only :/

Got the answer but it doesn’t look nice ;(

I agree, not nice, not satisfactory.

I misread the question as “should ‘x’ be in the following sequence. That confused me for a moment but when I had the right question, I solved it pretty quick (around a minute) and even instantly thought of how to write the answer BECAUSE of my misreading of the question in the first place…

Less than 1 minute figured out, but I think there is more than one answer

Not sure if I have the correct answer but if I have, it took me 3mins. Slooooow compared to everyone else, huh? :D

Yes!

Have an answer almost instantly, but I couldn’t type it if I wanted to…

I find I can type it – just didn’t bring enough imagination to it.

Had no clue after reading the puzzle. Bus solved at a glance after reading the comments.

I got it in under a minute but that’s not to say I found it easy. Was baffling at first. Good puzzle!

Same as rmb; was stumped but first few comments had me looking in the right direction…!

I think I solved it. The problem is I don’t know how to type it :(

Same problem. It works a bit better if you’re a bit open-minded about what x can be.

I have an answer that works, but feel there may be more than one. Under a minute.

Took me about two minutes – I’d like to say it was very clever, but I actually felt like a bit of an idiot when I found the answer!

I normally don’t like those kinds of puzzles. But this one was easy to get my head around after about a half minute

It can even be solved on small phones, as long as they aren’t too much down to earth.

Took a couple of minutes and then it clicked,look at the numbers.

Hey, where did you get my phone number?

About 20 seconds

I feel a bit slow now reading those comments. Love the Friday puzzle, this one took me the longest so far.

Equally pleasing and irritating when you get it though.

About 30 seconds of looking for a pattern before I spotted what was going on.

While it’s possible to construct a formula to generate that sequence with almost any number at x, I think, having found it, it’s obvious which one the problem setter had in mind.

Took about a minute, very cute. Although using numbers isn’t quite a perfect fit

Less than a minute. It’s a bit late to be doing these sorts of puzzles.

felt like a plum when i finally saw it.

not entirely sure how to display it though?!

Yay got it, probably wouldn’t have though If I hadn’t read the comments.

Got it immediately. Having watched a certain episode of Only Connect may have helped though.

Very nice, fastest one yet for me (75 seconds) :D

Got it in about 60 seconds, but only because I wrote the sequence down on a sheet of paper in a single column, (hint!)……

Got it instantly but had the help of the first comment :)

Good one.

Got it! Finally, was L8 by 5 min!

No, you’re three days early..

I see what you did there, Engywuck ;)

quite simple, really. If you take the function

f(x) = 11 x^6-3476 x^5+417956 x^4-23727440 x^3+639051776 x^2-7194463232 x+24770887680

and solve for all f(x)=0 you find that x= 16, 06, 68, 88,

40, 98Daryl may be right but there is an unlimited number of such functions that, on solution, will give an unlimited number of solutions.

In other words: you can pick an answer and construct a polynomial that will give you your chosen solution. That’s tantamount to cheating!

Daryl, I think you’re over-thinking the solution :)

Savant and mittfh, read the sarcasm sign

That said, I still don’t have the solution…

Ok, got it now

yeah – I did it the same way.

About 10 seconds, one of those “easy if you’ve seen these type of puzzles before” puzzles.

Struggled with it for a few minutes and couldn’t get it, I even checked the web page, rather than the RSS feed, in case there was a corrected typo. Came back a couple of hours later and saw it straight away. I don’t understand how I missed it the first time round.

Some unicode characters might help: ∠ or maybe this Ł

This is a bit naughty. I had already got it, but I rather fancy your comment is too much of a spoiler.

Of course, that may only be because I have already ‘got it’.

Very good, haha.

Nice one. :)

Took me 2-3min to look into all possibilities and to solve it.

About 30 secs, 25 of them before deciding to write it down

About 10 seconds to realise there wasn’t a mathematical solution using the numbers as presented.

Knowing from previous experience Richard can be quite crafty, I mentally changed my viewpoint and quickly arrived at the most probable solution (although it does break the symmetry of the provided numbers).

So about half a minute in total – my quickest yet :)

I think there are an infinite number of solutions using the pattern that I have spotted.

Forget that. I just got it.

To those who despair, put that frown upside-down.

…. What? Did I say too much? ;-)

Back on topic, it took me time to solve this. Someone in the comments said something about writing the above numbers down in a single column, and even then, it took a few minutes before it slowly dawned on me what was going on. Simply put, forget about mathematical formulas, you just need to step back and see things from a different angle.

Also, writing the numbers down in the classic calculator style doesn’t hurt, either.

No, the “1” doesn’t work.

As I see it, the answer isn’t a “value” at all.

a string is a value. the answer is a value… hope i didn’t give too much away.

20 seconds gets me eight quid! I wish that was my usual rate…

hahaha i get it

Hmm. I’ve got an answer, not entirely happy with it, because it doesn’t quite look right, but it fits. I’ll have to wait for Monday.

Took me about 5 mins, couldn’t see it straight away, so I did what I often do with these puzzles; walked away and when I came back I got it in about 30 seconds.

I usually skip the math ones, but I stuck with this one long enough to see the trick. About a minute. Good one.

Got it in about 10 minutes of making my head hurt.

I don’t know. I think I’m just too late.

just under 90 seconds.

Less than 10 seconds. It’s the sort of spin that some people notice immediately. On the other hand, why is the time important? As Professor I.M. Gelfand used to say, “you have to be fast only to catch fleas”.

Think I got it not too hard but made me think.

Five seconds.

Ha Ha, didn’t get it at all until I gave up and looked at the comments.

Finding it funny how so many people can’t resist showing off that they have the right answer by giving overly-obvious clues. Interesting. Glad I solved it before looking at any comments (about 10s).

I got the principle in about 10 seconds, then struggled over the first character – in the end I had to write it down to “work out” the first character

Nice puzzle, I solved it and it gave me some satisfaction.

I’m annoyed by the way that so many people write down how long it took them to solve it. Surely the joy of these puzzles and problems is in working them out, not in solving them quickly or more quickly than others.

Rufus: Richard invited people to let him know if they have solved it and how long it took them to complete the puzzle, now he also knows how many people didnt read the instructions.

yeah, I saw that after I posted. Think it’s a bad idea. Is the motivation to do these puzzles in the ego-boost of solving them quickly or in the pleasure of solving them? Maybe people could comment on whether they enjoyed the puzzle and why.

I enjoyed the challenge of this one, and the neatness of the answer.

Less than 2 minutes. Good one indeed.

You guys are all crazy – it’s just a bunch of random numbers. Meaningless. I’m not falling for th

Oh look! Look at that! Nice!

In your face, world! Who’s the daddy?

Perhaps two minutes. Clever puzzle. Very happy to have solved it.

Came to me in a couple of minutes. Feel quite clever now.

I came to the answer quickly when I remembered that the question was first set for Dorothy by the Wizard of Oz

haha!

Thank you, my Lord.

About 2 minutes. Nice! :D

I would imagine Australians will see this straight away.

Wow! Very impressed with myself – saw it after about 15 seconds. I hardly ever solve them usually.especially when they’re number based.

Luckily I am sick. Scribbled down the numbers before going back to bed, then looked at the note. Easy.

Took me about a min but was very simple – reminds me of whats it called… the thatcher effect? I think… Something along those lines

Fun one! After following the Friday Puzzles for a bit, you know that you need to think outside the box to solve some of them. After reading the first couple of comments, I got it right away.,

87

How?????

87

87