Question

Elaine used the subtraction algorithm to subtract −17−(−3). She got the answer −14, but she does not feel confident that she is correct. Connect the expression −17−(−3) to a two-color counter model. Explain how the two-color counter model can be used to confirm whether Elaine’s answer is correct.(2 points)

Answer 1

To model the expression −17−(−3) using a two-color counter model, we can use two sets of counters: one set representing -17 and the other set representing -3.

First, we start with 17 counters of one color to represent -17. Then, we take 3 counters of the opposite color to represent -3.

To subtract -3 from -17, we remove 3 counters of the opposite color from the 17 counters. This leaves us with 14 counters of the original color, which represents -14.

Therefore, if we count the final number of counters and it matches Elaine's answer of -14, then her answer is correct. If the number of counters is different, then her answer is incorrect.