Changing temperatures 0 Overview Using this Resource Connecting to the Curriculum Marking Student Responses Working with Students Further Resources This task is about addition and subtraction with negative numbers. Question 2Change answer a) On Friday morning the temperature was ⁻2°C. By the evening it was ⁻11°C. By how many degrees did the temperature change during Friday? °C b) On Saturday evening the temperature was 6°C. On Sunday morning it was ⁻7°C. By how many degrees did the temperature change during the night? °C Question 1Change answer c) At midday on Monday the temperature was 7°C. By the end of the day it had decreased by 15°C. What was the temperature at the end of the day? °C d) On Tuesday morning the temperature was ⁻4°C. By the afternoon it had increased by 9°C. What was the temperature in the afternoon? °C e) On Wednesday evening the temperature was ⁻5°C. By Thursday morning it had decreased by 8°C. What was the temperature on Thursday morning? °C Copyright: Image: J.Fisher [permission for educational classroom use in Aotearoa] Level: 4 Curriculum info: Maths, Number and Algebra, Number Strategies Keywords: negative numbers, addition, subtraction Description of task: Using temperatures, students perform addition and subtraction calculations involving negative numbers. Answers/responses: Y9 (03/1999) a) i) ii) 9 or ⁻9 13 or ⁻13 easy moderate b) i) ii) iii) ⁻8 5 ⁻13 moderate moderate moderate Diagnostic and formative information: Common error Likely calculation Likely reason a) i) b) i) ii) iii) 13 22 13 13 2 + 11 7 + 15 4 + 9 5 + 8 Adds the absolute value of both numbers (i.e., ignores negative signs and subtraction altogether). a) i) ⁻13 ⁻2 – 11 Adds ⁻2 and ⁻11 instead of subtracting them. a) ii) ⁻1 1 6 – 7 7 – 6 Adds 6 and ⁻7 instead of subtracting them. Uses 7 instead of ⁻7. Positive and negative number line Ordering temperatures