C question : Why here i need to put parentheses

Question

float​ ​index​ = ​0.0588​ * (​100​ * (​float​)y / (​float​)x) - ​0.296​ * (​100​ * (​float​)z / (​float​)x) - ​15.8​;

Why i need to put parentheses around float

Answer 1

y, x and z were converted to float. The use of parentheses are part of the conversion syntax.

https://www.tutorialspoint.com/cprogramming/c_type_casting.htm

Answer 2

() called cast operator
https://www.ibm.com/docs/en/zos/2.1.0?topic=expressions-cast-operator