I honestly don't recall hearing the the term decimal fraction either during my pure and applied A'level maths and definitely not whilst at univerversity. That said, both were a gazillion years ago.
When I was at uni (also initially a gazillion years ago, although I've done some higher degrees more recently than that) it was very straightforward:
• "decimal" meant that a number is represented using the decimal number system - i.e. using digits 0-9 and with 'place values' within the number (both before and after any decimal point) differing by powers of 10.
•"fraction" simply meant non-integer, however represented.
... hence 123.456 was a "decimal fraction', since it was non-integer and expressed in the decimal number system
According to Google a decimal fraction is one where the denominator is a factor of 10. So... 0.5 would be expressed as 5/10.
I'm not familiar with that use of the phrase, and it certainly did not have that meaning 'back then'. As above, it would probably not even have been regarded as decimal since, although numerator and denominator are both (I assume!) expressed in terms of the decimal system, the expression as a whole is not.
I was taught that a vulgar (improper) fraction was one where the nominator is larger than the denominator, eg 5/2.
In my day, that was called an "improper" fraction, "vulgar fraction" (or "simple fraction", or "common fraction") was any quantity expressed as a numerator divided by a denominator, using any number system for the two elements (I have vague recollections of having to play with "vulgar fractions" in which both numerator and denominator were octal, or maybe hexadecimal!)
Definitions on the web seem to vary, so I guess it depends on how old one is and where they were taught.
Agreed. My A-Levels and S-Levels (which included both Pure and Applied Maths) were best part of 60 years ago, and my initial uni education soon after that, but I also did some higher degrees in mathematical subjects some 25-30 years later - but all of that is 'pretty old'.
But hey, maths is not a perfect science, as is evidenced by paradoxes such as Gabriel's Horn. An infinitely large cone which, if filled with paint, would not contain enough paint to cover the outside of the cone.
Indeed, but one doesn't need to have had a very high level of mathematical education to have encountered that. The fact that a rotated curve could result in a cone of infinite surface area but finite volume was one of the early things we were exposed to when we started learning calculus for O-Level 'Additional Maths'.
And don't get me started on imaginary numbers...
Potentially mind-boggling, but extremely useful, even in electronics
