The mean temperature for the first 7 days in January was 6 degrees. The temperature on the 8 days was 10 degrees . What is the mean temperature for the first 8 days in January?

The mean temperature for the first eight days is 6.5 degrees

Step-by-step explanation: The most important piece of clue has been given which  is the mean (average) for the observed data set, which is 7 days.

Note that the formula for the mean of a data set is derived as;

Mean = ∑x / f

Where ∑x is the summation of all observed data set and f is the number of data observed, that is 7. The formula now becomes;

6 = ∑x / 7

By cross multiplication, we now have,

6 * 7 = ∑x

42 = ∑x

This means the addition of all temperature observed on the first 7 days is 42. The temperature on the eighth day is now given as 10 degrees, this means the summation of all observed data for the first eight days would become 42 + 10 which equals 52. Therefore when calculating the mean for the first eight days, ∑x is now 52. The formula for the first eight days therefore is derived as follows;

Mean = ∑x / 8

Mean = 52 / 8

Mean = 6.5

The calculations therefore show that the mean temperature for the first eight days in January is 6.5 degrees