the original question is

In a shop, the selling price of three items are $49.3 $54.9 and $82.2

(a) By rounding up the selling price of each item to the nearest dollar, estimate the total selling price of the three items.

It's easy. No problem . Total = 49+52+82= $186

(b) A person has $190. Will he have enough money to buy the three items? Use the result of (a) to explain your answer.

That comes to a problem. At the first glance the answer should be $190-186 = 4 and so "YES, enough"

but in fact, some of the items in (a) is rounded down....so it is possible that the money is not enough because in fact the items

will not be sold to the nearest dollar, so why using the result of (a) to explain the answer of (b) makes sense?

Thank you.