How can you express 499 to find the product 499 x 5 using mental math? explain

We can write 499 as 499 = 500 - 1

Because it is easy to multiply 500 and 5 compare to 499 to 5.

So product of 499 * 5 = (500 - 1)*5
                                   = 500*5 - 1*5
                                   = 2500 -5 = 2495

So the answer is 2495.