Final answer:
Using number sense, you can infer that the exact answer is greater than $600 if you are adding numbers greater than $600 individually, or if multiple items each cost more than $19 and there is a substantial quantity involved.
Step-by-step explanation:
To determine that the exact answer has to be greater than $600 using number sense, you can look at what you already know about the numbers involved in the context provided.
If you are adding together numbers that are already greater than $600 individually, such as in the given example where we consider the summing of 611 and 1027, you can infer that the sum of these numbers must also be greater than $600 since both numbers are individually greater than this amount.
This is analogous to knowing that the sum of two positive numbers is always greater than each of the numbers individually.
Additionally, if we know that each of the T-shirts costs more than $19 and a group of people own multiple such T-shirts, we can instantly infer that the total cost would exceed $19.
So, if the number of T-shirts or any other item counted is substantial, the total cost will easily exceed $600.