YOU SAID:
My brother ate 5 and a half hotdogs yesterday
INTO JAPANESE
私の兄は昨日5つ半のホットドッグを食べました
BACK INTO ENGLISH
My brother ate five and a half hot dogs yesterday
INTO JAPANESE
私の兄は昨日5匹半のホットドッグを食べました
BACK INTO ENGLISH
My brother ate five and a half hot dogs yesterday
That didn't even make that much sense in English.