Probability and Stats

Question

There are 49 even numbers from 1 to 99. The mean of 48 of these numbers is 49 and 5/12. Which even number was not included in the calculating of this mean?

Answer 1

the total sum of all 49 should be

49/2(2 + 98) = 49/2(100) = 2450

the total sum currently is

(49 + 5/12)*48 = 49*48 + 5/12*48 = 2352 + 20 = 2372

meaning that the missing even number here is

2450 - 2372 = 78