# Grandpa's Crazy Math II: Another Grandpa Mystery

Grandpa says: "This is really a stretch but

Prove to me

S = 0.5 or 1/2

Grandpa and his very lateral thinking!

• Just out of curiosity : Rot13(Znl or vaireg vg naq fnl F.0 = F) – Ak19 Aug 8 '19 at 12:07
• Clever but I am looking for 1/2 – DrD Aug 8 '19 at 12:20
• Could this have something to do with Shear Stress? Shear stress in fluids to be specific. – Abbas Aug 8 '19 at 12:39
• No @Abbas. Grandpa is not that engineering minded. Just crazy. – DrD Aug 8 '19 at 12:42

Maybe Grandpa starts with

SIX = VI

and then (oh no no)

$$S = \frac{VI}{IX} = \frac{V}{X} = \frac{1}{2}$$ (by treating the letters as products and cancelling the $$\small I$$'s).

A stretch - but Grandpa's been flexible before: Why would five hundred and five be same as one?

• Bulls Eye! Great Lateral Thinking @Tom – DrD Aug 16 '19 at 11:38

It is possible that Grandpa deduces his claim from

The numbering on the models of the iPhone (listed here)

Explicitly, the iPhone numbering according to generation is as follows:

1st gen - iPhone
2nd gen - iPhone 3G
3rd gen - iPhone 3GS
4th gen - iPhone 4
5th gen - iPhone 4S
6th gen - iPhone 5 (and iPhone 5C)
7th gen - iPhone 5S
8th gen - iPhone 6 (and Plus)
9th gen - iPhone 6S (and Plus)
10th gen - iPhone 7

If Grandpa were to reasonably assume that the model numbering up to this point follows an arithmetic progression, then it would be fair to say that $$S$$ represents $$0.5$$ or, indeed, $$\frac{1}{2}$$. That is, for example, iPhone 5S is really iPhone 5.5

Of course, the progression is broken in the next generation with iPhone 8 but the argument can still be made that if an intermediate version between iPhone $$N$$ and iPhone $$(N+1)$$ is constructed then it takes on the numbering scheme iPhone $$NS$$ which we can reasonably assume to be equivalent to iPhone $$(N+\frac{1}{2})$$ as it claims a generational position of its own without bias towards its predecessor or descendant.