What does “hard sums” mean?

I have heard British people speak about "hard sums," but I can't find a definition anywhere. Is it just a generic way of referring to any arithmetic that the speaker believes is difficult? Or does it have a more specific definition or nuance?

If someone says "I can do hard sums," what does that mean exactly?

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Why are all the answers getting downvoted? –  no one special Jun 23 '11 at 13:06

"Hard sums" is used to mean "difficult mathematics" in a self-deprecating way, depending on the speaker.

If someone says

I can do hard sums.

and they are:

• A four year-old: It means they've started doing addition.
• An eight year-old: It means they've mastered multiplication.
• A high-school student: It means they can do some simple calculus.
• An undergraduate: It means they can do more complex calculus / analysis / algebra.
• A post-graduate: It means they're Einstein. :-)

And each group is more self-deprecating than the last.

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So it's just a way of saying "difficult math"? No specific idiomatic meaning? Not even a nuance? –  no one special Jun 23 '11 at 4:52
AFAIK, the only nuance is what I mentioned: it's self-deprecating. –  Peter K. Jun 23 '11 at 11:48
@Down-voter: Feedback on why you down-voted appreciated! –  Peter K. Jun 23 '11 at 11:54
Interesting. When I saw this used, it was speaking to a broad audience with a presumably wide range of math levels, so it seemed like it must refer to something specific. Also interesting that it means any kind of math. The word "sums" gave me the impression that it referred to arithmetic. A bit disappointing that it has such a bland meaning, but thank you. :-) –  no one special Jun 23 '11 at 12:46
@no one special: I'm sorry to disappoint! My perspective is from when I was an engineering grad student who used to hang around with mathematics grad students. Others may have a different view. In general, the math grad students found bistromathics harder than what they did for a living. :-) –  Peter K. Jun 23 '11 at 12:55