The Singh family lives in a housing development full of Scientists and engineers (god forbid!). The Home Owners have come up with weird ways of numbering their houses.

K Street is all engineers and M street is all mathematicians.

Turns out Mr. Singh is an engineer and of course Mrs. (Dr.) Singh is a Mathematician! So they have a house at the corner of K and M street.

So assuming they followed the patterns for both streets, what is their house number?


Engineers like "Metrics" Think Metric Measurements and !

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  • 1
    $\begingroup$ You have to think laterally with respect to which street? $\endgroup$ Aug 6, 2019 at 16:18
  • $\begingroup$ That would be a clear hint @Arnaud Mortier $\endgroup$
    – DrD
    Aug 6, 2019 at 17:25
  • $\begingroup$ But a very good question none-the-less $\endgroup$
    – DrD
    Aug 6, 2019 at 17:26
  • $\begingroup$ rot13(gur yrggre rz vf bar gubhfnaq va Ebzna ahzrenyf, naq gur yrggre xnl va ybjre pnfr vf gur zhygvcyvre sbe bar gubhfnaq va gur zrgevp flfgrz), but I don't know what to do with that information. $\endgroup$
    – shoover
    Aug 7, 2019 at 2:53
  • 1
    $\begingroup$ Judging by the correct answer, #1 K street should actually have no number at all... $\endgroup$ Aug 12, 2019 at 20:08

5 Answers 5


I think the house number is


Since K street is all engineers,

In Roman Numerals, 1000, 100, 500, and 1 translate to M, C, D, and I. When combining these with a metric measurement (metres) per @DEEM, we see that we get MM (millimetres), CM (centimetres), DM (decimetres), and M (metres) which are increasing units of length. Thanks to @Levieux for the assist!

Since M street is all mathematicians,

In Roman Numerals, M translates to 1000, which could mean that all house numbers (ie. 1000, 2000, 6000) are all multiples of 1000. @Braegh has further noted that the house numbers follow the pattern x! times 1000, as 1! = 1, 2! = 2, and 3! = 6. Thanks, @Braegh!

The house number

1000 meets both criteria.

  • 1
    $\begingroup$ Membrane Capacity___ It is lot simpler @El-Guest $\endgroup$
    – DrD
    Aug 7, 2019 at 1:13
  • $\begingroup$ How does the updated answer look, @DEEM ? $\endgroup$
    – El-Guest
    Aug 7, 2019 at 2:07
  • $\begingroup$ Also, rot13(Jvgu 1000, gurer pbhyq nyfb or n frdhrapr va gur Z fgerrg ubhfrf, bs gur sbez ((cerivbhf ubhfr ahzore/1000)^2)*1000 + (cerivbhf ubhfr ahzore)) $\endgroup$
    – Stiv
    Aug 7, 2019 at 8:45
  • 1
    $\begingroup$ I think the M street pattern is rot13(1000 gvzrf k!, jurer k vf gur ahzore bs gur ubhfr, fgnegvat sebz gur pbeare. Gur arkg bar jbhyq or gjragl-sbhe gubhfnaq, va guvf cnggrea.) $\endgroup$
    – Braegh
    Aug 11, 2019 at 23:26
  • 1
    $\begingroup$ The Roman numeral part holds for mm, cm, and dm, but you gloss over the fact that im isn't a unit. $\endgroup$ Aug 12, 2019 at 13:05

Partial answer.

I believe the answer is



the engineer sequence turned in roman numerals would then be LCDI, which is engineer slang for Leakage Current Detection And Interruption.


A mathematician will tell you that there are billions of good reasons 50, 2000 and 6000 could be consecutive terms of a sequence, although OEIS has no results (perhaps that's what makes it special: it's the only sequence of three $\leq 4$-digits numbers that OEIS doesn't know an extension of :) )


I think the answer is


Because on M street:

If you convert to roman numerals, each house has two characters with one being an M $\rightarrow$ MM = 2000, $\overline VM$ = 6000. So the Singh's house could be CM = 900, MI = 1001, MV = 1005, MC = 1100, MD = 1500, etc.

Because on K street:

The letter K represents a thousand. It doesn't make sense to represent a number under 1 or over 999 with a K. Therefore the number is limited between 1 -> 999. This leaves CM = 900 as the only remaining house number.

  • $\begingroup$ How is VM=6000? $\endgroup$
    – JMP
    Aug 7, 2019 at 4:12
  • $\begingroup$ @JonMarkPerry I think like this: $\overline VM$? $\endgroup$
    – user61820
    Aug 7, 2019 at 4:20

Converting my Aug 7 comment into an answer:

The house number is


because on M street:

the letter M is one thousand in Roman numerals

and on K street:

the letter K in lower case is the multiplier for one thousand in the metric system

  • $\begingroup$ Then how do you explain the other house numbers @shoover? What pattern? $\endgroup$
    – DrD
    Aug 11, 2019 at 20:11


I don't actually have an answer, yet. Here's something, though:

K could be kilo and M could be mega as both have something to do with numbers and it looks like the numbers on K (kilo) Street are smaller than the numbers on M (mega) Street by a factor of 10, so... maybe 1,000 to mark the transition point?

Might be worth noting that

K and M can be kilometers, as well, which is another metric measurement...

  • $\begingroup$ On the right path. Think another metric measurement. Your answer (number) is correct though, just like @El-Guests $\endgroup$
    – DrD
    Aug 11, 2019 at 11:03
  • $\begingroup$ @DEEM - Am I still on the right path? Have I advanced? Did I go backwards? $\endgroup$ Aug 11, 2019 at 23:09

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