Question

David added 2 and –3 using the number line tool. Which of the following errors did he make?
He started at 2 instead of zero.
He moved right 2 units for positive 2.
He moved right 3 units for negative 3.
He started at zero instead of 2.

Answer 1

To solve the problem, let's analyze how to properly add the numbers 2 and -3 on a number line.

1. **Start at zero**: When adding numbers using a number line, typically you start at zero, unless stated otherwise.
2. **Move right for positive numbers**: For the positive number 2, you move right 2 units from your starting point (which is zero).
3. **Move left for negative numbers**: For the negative number -3, you then move left 3 units from your new position.

If David made an error by starting at 2 instead of zero, he would then incorrectly do the following:
- Starting at 2 (not zero), moving right 2 units for the positive value would take him to 4.
- From 4, moving left 3 units (for -3) would take him to 1.

This means that the main error he made was **starting at 2 instead of zero.**

So, the correct answer is:
**He started at 2 instead of zero.**