999 999 999 990
12
It is 891.
999999999999
987654321
9999
12
It is 891.
99x9999=989901
9999 is the 4-digit number and 999 is the 3-digit number.
999999999999
-2
987654321
9999
998.
999,999,999,990
The greatest possible number that a 5-digit combination can form is 99999. This is achieved by using the highest digit, 9, in each of the five places. Therefore, the largest 5-digit number is 99999.
You will get the greatest product if you choose the greatest possible numbers in both cases, i.e., 9 x 99.