Hi Diti,
not really, there is just one new tyre in that odd size and it is a slick:
That depends on your wheels (please don’t think that all 18" Strida wheels are equal regarding their centers; there are ones a mm right and other ones a mm left of center) - that’s why some riders reported yes and others said no.
I’d not recommend to use them - consider that a slightly untrue wheel might cause periodically rubbing at the frame. 
You’re right with math but don’t overlook tolerance 