Question

The mean temperature for the first 4 days in january was 1°C. The mean temperature of the first 5 days in January was 2°C. What was the temperature on the 5th day?

Answer 1

Answer:

Step-by-step explanation:

mean is average, so if we label the first through fifth days of january a-e we can solve it.

So average of the first four is (a+b+c+d)/4 = 1 and the first five is (a+b+c+d+e)/5 = 2.  Since it's easy, let's get rid of the fraction in both.

(a+b+c+d)/4 = 1 and (a+b+c+d+e)/5 = 2

a+b+c+d = 4 and a+b+c+d+e = 10

Now, we know a+b+c+d is 4, so we can replace that in the second equation

a+b+c+d+e = 10

4 + e = 10

e = 6

ad since e is the fifth day, we know the temperature of it.  Let me know if something here didn't make sense.  

Answer 2

Answer:

  6 °C

Step-by-step explanation:

The total of all temperatures for the first 4 days is 4 times their mean:

  4 × 1 °C = 4 °C

The total of temperatures for the first 5 days is likewise the number of days times the mean:

  5 × 2 °C = 10 °C

The only thing added to the total of the first 4 days to give the total for 5 days is the temperature on the fifth day: 6 °C.

_____

4 + 6 = 10