* is not a standard math symbol
Both the * and the # (Octothorpe) are Math symbols and each is used in different contexts.
Usually the * stands in basic math for multiplication, but a raised asterisk (like "a" raised to the power *) denotes an adjoint or a complex conjugate.
A doubled asterisk ** is sometimes used for non commutative multiplication.
The Hash or the Octothorpe among others stands for Cardinality. eg #A denotes the cardinality of the set A.
Also # is used to denote a Primorial, the Factorial for Prime numbers.
PS: The above is not related to the Grade 4 problem. Just FYI.
But do kids in year 4 ever encounter the * or the # ?