Question

the mean temperature for the first 4 days in January was 9°C the mean temperature for the first 5 days in January was 7°C. what was the temperature on the 5th day?

Answer 1

Ok to make this easy, do 4 days as 9°C. So 9+9+9+9=36 / 4 = 9. So that's the first 4 days. Then the 5th day, the mean dropped to 7°C so that means the temperature dropped. -1 is your answer and you can check this by doing 9+9+9+9+(-1) = 35 / 5 = 7°C.

Answer 2

-1°C

Explanation:

`Mean = \frac{\text{Sum of all observations}}{\text{No. of observations}}`

Now we are given the mean temperature for the first 4 days in January was 9°C

So,
`9 = \frac{\text{Sum of temperatures of first 4 days}}{4}`

`9 * 4 = \text{Sum of temperatures of first 4 days}`

`36= \text{Sum of temperatures of first 4 days}`

Now we are given that the mean temperature for the first 5 days in January was 7°C

`7 = \frac{\text{Sum of temperatures of first 5 days}}{5}`

`7 * 5 = \text{Sum of temperatures of first 5 days}`

`35= \text{Sum of temperatures of first 5 days}`

So, Temperature on 5th day = Sum of temperatures of first 5 days -Sum of temperatures of first 4 days

Temperature on 5th day = 35°C-36°C = -1°C

Hence the temperature on the 5th day was -1°C