Does hearing or reading about something qualify as experiencing it?

The term "experience" is being misused, here. Generally it applies not to perceived objects, such as apples, but to life episodes, such as a car accident. One experiences something which one can "go through", e.g. pregnancy, or labor, or a hard breakup. One who "has experience" is someone who has been through or done things before.

The proper term to use when talking about the physical referents of concepts is not "experience", but "perceive". It's wrong to say "I experience an apple." An apple is not an episode. One might say: "I experience the perception of an apple" but that's needlessly complex. "I perceive an apple" is correct.

When you hear a story of a man being mugged, you do not experience the mugging. To say so would obliterate the difference between being a victim, and being an audience member in the telling of a story. The audience member imagines the mugging. He does not experience it.

Likewise, being told about a particular kind of apple doesn't count as the perception of that kind of apple. One man perceives it, and describes it to another man, who does NOT perceive it. He might imagine it, but that's not the same as perception. The imagining man experiences his imagination of the apple -- or to say it without awkwardness: the man imagines the apple.

As for complex math concepts, they are, properly, rooted in perception. They are just very abstract, so there are many layers of concepts between them and first level concepts.