What is the greatest possible number of digits in the product of a 4-digit whole number and a 3-digit whole number?
I need to find the largest possible product of a 4-digit whole number and a 3-digit whole number, and then count how many digits it has. To get the largest possible product, I want to maximize both factors. The largest 4-digit whole number is 9999, and the largest 3-digit whole number is 999. So the largest possible product is 9999 times 999. 9999 times 1000 is 9999000, which has 7 digits. 9999 times 1 is 9999, which has 4 digits. To subtract 9999 from 9999000, I need to align the digits and borrow from the left. So the largest possible product of a 4-digit whole number and a 3-digit whole number has 7 digits.

