Solidity integer division of different sizes

Question

I'd like to divide integers of different sizes (uint16 and uint256). Do I need to cast the integers to the same size prior to the divide? Or can I just do the the following safely:

    import "../math/SafeMath.sol";
    using SafeMath for uint256; 
    using SafeMath for uint16;

    uint16 public totalValid;
    uint256 public etherValue;

     function _calculatePayout() internal{
        require(this.balance > 0); 
        etherValue = this.balance.div(totalValid); // uint256 this.balance
    }

Thoughts appreciated.

Answer 1

Usually these libraries are written and used for one particular integer type, so in your case you have to use SafeMath for uint256 and typecast totalValid.