In July, the average temperature in one US city was 29°C. By December, the average temperature had fallen by 29°C. Explain why the average temperature in December was 0°C.
The temperature went up 29°C, which represents a positive 29. Then the temperature fell 29°C, which represents a negative 29. The average temperature rose and fell the same amount. The absolute values are the same, so the difference is 0.
