True, but you said a person with IQ 90 has the same ability as a person with 150. I disagree with that. In general that is not true.
The correlation is not so linear
There are everal books that explain the concept of IQ and how it works
People with higher IQ has not necessarily supeior numerical or mathematical abilities
As a matter of fact when you join the Mensa you're told in what "matter" your IQ capabilities are higher
It could be visual perception, ideas correlations, language, deduction
In fact not only a vast majority of people with very high IQ has not particular mathematical ability but majority of people who got a Ph.D. in mathematics, arithmetical or algebra has an average IQ or slighly higher
It's interesting to no how lot of composers considered geniues in music where completely average or bad in other matters
There are several letter by Mozarto to his father when he complaint about how natural rhythm is to him but how tough is for him to find the mathematical explanation to it (referring to his teaching to de Guines)
So, no, Mozart was not perticularly keen on mathematics, algebra or geometry for that matter
I doubt that composers of the past had all higher IQ especially after reading about their life and their knowledge
What is known for sure is that having an higher IQ is not synonimous with knowing everything and always getting high grades at school
Quite the contrary, many people with higher IQ where considered stupid and dull and were particularly bad in many common matters despite being genious in their own abilities
Daniel