Hindu-Arabic numeral for 5
This is probably not how we get our ‘ B ' Hindu-Arabic notation is strictly positional. It means if we stick an Arabic ‘٤' (4) to the left of an Arabic ‘١' (1), we would normally get a ‘٤١' (41). $$4\times 10 + 1 = 41$$ If for one moment, suppose the glyph for ‘5' is yet to be invented and we are asked to supply one. Excuse me, how do you write ‘five'? One easy way is to copy the Romans: We pretend the rule is not positional but additive, i.e. $$٤+١=4 + 1 = 5$$ However, for our new design to function properly (and to prevent mix-up) in the positional scheme, they must be fused tightly together into one single glyph. And the result is something that looks like a mirror image of B ( B ) or a Gujarati ‘ઇ' (i). ٤ ١ Now, this gedankenexperiment can be repeated if you start with ઇ (5) and remove the vertical stroke (1) on the right to get 4 (٤).