Question

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