72519 x 9999 = 72519 x (10000 - 1)

= 72519 x 10000 - 72519 x 1

= 725117481

To solve this question, we can use the multiplication formula for two numbers that differ by one, i.e., (a)(a+1) = a^2 + a. We can break down 9999 into 10000 - 1 and use this formula to simplify the multiplication.

72519 x (10000 - 1)

= 72519 x 10000 - 72519 x 1 (distributive property of multiplication)

= 725190000 - 72519 (simplifying)

= 725117481

Therefore, the correct answer is option A, 725117481.

Here are some relevant definitions and formulas that we used:

• Multiplication: a mathematical operation used for finding the total when a specific number is added to itself a certain number of times.
• Distributive property of multiplication: a(b + c) = ab + ac. This property allows us to multiply a sum by a number and get the same result as multiplying each addend by the number and then adding the products.
• Square: the result of multiplying a number by itself. For example, 3^2 = 3 x 3 = 9.
• Formula for multiplying two numbers that differ by one: (a)(a+1) = a^2 + a. This formula can be useful for simplifying multiplication when one of the numbers is close to a multiple of 10 or 100.

In this problem, we used the distributive property of multiplication and the formula for multiplying two numbers that differ by one to simplify the multiplication of 72519 and 9999.