Question

which number - line model represents the sum of 1.25 + (-0.75)? a. b. c. d. (number lines as shown in the image)

Explanation:

Step1: Calculate the sum

First, calculate \( 1.25 + (-0.75) \). This is equivalent to \( 1.25 - 0.75 = 0.5 \).

Step2: Analyze the number - line models

• For a number - line model representing \( a + b \), we start at \( a \) and then move \( b \) units (to the right if \( b>0 \), to the left if \( b < 0 \)). Here, we start at \( 1.25 \) and move \( 0.75 \) units to the left (because we are adding a negative number).
• Let's analyze each option:
• Option A: The starting point and the direction of movement do not match the calculation.
• Option B: The starting point and the movement do not correspond to \( 1.25+(- 0.75) \).
• Option C: The starting point and the movement do not match our calculation.
• Option D: We start at \( 1.25 \) (on the number line) and move \( 0.75 \) units to the left, which should land us at \( 0.5 \). The number - line in option D shows a starting point and a movement that is consistent with \( 1.25+(-0.75)=0.5 \).

Answer:

D