I need a help for: How will you declare an array of three function pointers where each function receives two integers and returns a float?

The simpler way (less error prone) is to use a typedef helper.

typedef float ((*YourFunction)(int, int);
   YourFunction YourArray[3];

or, if you wish code that is terse but easier to get wrong (typos very easy), use this;

float (*YourArrayAlternative[3])(int, int);

to declare an array named YourArrayAlternative.

Whichever way you choose to do it, I'll leave it to you to work out how to initialise array elements.