The apartment building where hannah lives was built with 213,854 bricks.

how many groups of 100,000 bricks can you make with 213,854?

So what this effectively means is 213854/100000

This gives 2.13854, or 2 with a remainder of 13854.

As you need complete groups the answer is 2, as the remaining 13854 cannot be used to make another group of 100000.