Use 0123456789 ten numbers to form two five digit numbers, how to combine the product to the maximum? Why does 96521 * 87430 have the largest combined product? Please explain the reason of this combination.

Use 0123456789 ten numbers to form two five digit numbers, how to combine the product to the maximum? Why does 96521 * 87430 have the largest combined product? Please explain the reason of this combination.

Use 0123456789 ten digits to form two five digit numbers. In order to find the maximum value of their product, we should first consider the maximum value of their sum. Undoubtedly, it should be a combination of 9 and 8 for ten thousand digits, 7 and 6 for thousand digits, 5 and 4 for hundred digits, 3 and 2 for ten digits, and 1 and 0 for ten digits