The average temperature for three days was 19 degrees. What must the temperature be on the fourth day to make the average temperature during the four days 21 degrees?

Answer 1

The average of 3 days temperature was 19 degrees:
[(x+x+x)/3]=19
x+x+x=3*19
x+x+x=57
let assume the three x values are 17, 21 and 19 which equal 57 degrees.
[(17+21+19+x)/4]=21
(57+x)=4*21
57+x=84
x=84-57
x=27
the 4th day temperature must be 27 degrees.

Answer 2

(T1+T2+T3)/3 = 19, T1+T2+T3 = 3*19 = 57. (57+T4)/4 = 21, T4 = 27 Degrees.

Answer 3

27 degrees