Răspunsuri

2014-11-06T11:36:51+02:00
S=n(n+1)/2
n=n(n+1)/2 * 5/100
n=n(n+1)/2 * 1/20
n=n(n+1)/40
40n=n(n+1)
40n/n=n+1
40=n+1
n=39