Answer:
Mean = 3.25°C
Step-by-step explanation:
The mean (or average) is given by the formula:
Mean = Sum/Number of Numbers
For first 7 days, the mean was 3, so we can say:
Mean = Sum/Number of Numbers
3 = Sum/7
Sum = 3 * 7 = 21
Then on 8th day, the temperature was 5, so the new sum would be (for 8 numbers):
New Sum = 21 + 5 = 26
Now we calculate the mean for 8 numbers:
Mean = 26/8
Mean = 3.25°C