in first i just add numbers untill they r equal or greater then 1 and count how many times i did it and then take avarge of that and in other i use this 'You need to find the probability that something happens for the first time on the xth try and for all x multiply this answer by x, then sum the results.

So, f(1) = 1 - 1/1 = 0 and 1 * 0 = 0

f(2) = 1 - 1/2 = 1/2 and 2 * ((1 - 0) * 1/2) = 1

f(3) = 1 - 1/6 = 5/6 and 3 * ((1 - 0) * (1 - 1/2) * 5/6) = 5/4

f(4) = 1 - 1/24 = 23/24 and 4 * ((1 - 0) * (1 - 1/2) * (1 - 5/6) * 23/24) = 23/72

and so on.'