In the strictest mathematical terminology, "How many ..." means:
"If you count them, what will be the last number you mention ?" .
principal(in terms of math)- the amount you borrow or deposit
HL in math mean hypotenuse leg
ask your math teacher
It
Polygon
sum means the answer of a math problem
A number? ^^
neither
the average
Dekagrams.
average
turning