Problema Solution
What is the average of the integers from 25 to 41?
Answer provided by our tutors
(25 + 26 + 27 + 28 + ... + 40 + 41)/(41 - 25 + 1) = (25 + 26 + 27 + 28 + ... + 40 + 41)/17
Since 25 + 26 + 27 + 28 + ... + 40 + 41 = 17*25 + (1 + 2 + ... + 16) = 17*25 + (1/2)(16*(16 + 1)) =
= 17*25 + 8*17 = 17*(25 + 8) = 17*33
(25 + 26 + 27 + 28 + ... + 40 + 41)/17 = 17*33/17 = 33
The average is 33.