we know that
The way to form the greatest number is to use the highest valued digit in the most significant digit.
so
[tex] 900,000,000+80,000,000+7,000,000+600,000+50,000+4,000+300+20+1=987,654,321 [/tex]
therefore
the answer is
The greatest whole number that uses all the digits from 1 to 9 only at once is
[tex] 987,654,321 [/tex]
