xcode NSNumber 转float 最后一位小数错误

 记录个还没分析的现象：

NSNumber *num = @0.47;

int val= (int)([num floatValue ]*100.0);

此时val 为46

NSNumber *num = @0.47;

int val= (int)([num floatValue ]*100);

或

NSNumber *num = @0.47;

int val= (int)([num floatValue ]*100.0f);

val才是47