So whole numbers include the negative numbers, the zero and the positive numbers. We will examine each category,
1- For the negative numbers: multiplying a negative number by a positive value will result is a negative value (negative values are less than positive values of course). Therefore, multiplying any negative number by 400 will give a negative value which will make the desired statement false.
2- For the zero: multiplying any number by a zero will give a result of zero which is again less than positive numbers. So, if we multiply 400 by a zero, the result will be zero which will again make the desired statement false.
3- For positive numbers: multiplying two positive numbers will result in a positive value. Since 400 is already greater than 15, therefore, multiplying 400 by any positive value will keep the statement true. Since we are looking for the smallest whole number, therefore, we will choose that number to be 1 which will give 400 when multiplied by 400 (this is the smallest possible value).
