An elementary school teacher that I work with shared a conversation that she had with one of her students earlier in the day during an after school curriculum user dinner. The student was working with a series of subtraction problems:
- 9-8=
- 15-8=
- 95-8=
- 105-8=
- 205-8=
The student shared that his answer to the first problem was 1; the second problem's answer was 7; the third answer was 87; the fourth answer was 97 and the fifth answer was "one hundred". The last answer puzzled the teacher.
Curious to determine what the student was thinking, the teacher questioned the answer of "one hundred" and encouraged the student to tell her more about the answer of 100. In doing so, the student revealed the following. "I know that 105-8 was 97. 205 is 100 more than 105. So 100 more than 97 is 197."
