For the first four days of a five day vacation, the mean temperature was 80 degrees. What must the temperature be on the fifth day in order for the mean temperature to be 82 degrees?

The 5th day must be 90

Step-by-step explanation:

The first 4 days averaged out to 80

You can find their total just by multiplying by 4. That won't tell you the exact values, but it will tell you their total when you add the 4 of them together.

80*4 = 320

Now you need to add another day into the mix. Call it x

320 + x

Now there are 5 days, not 4, and the new total is 82.

(320 + x) / 5 = 82          Multiply both sides by 5

5*(320 + x) / 5 = 82 *5

320 + x = 410                 Subtract 320

-320        -320

x = 90