Question

Cate numere naturale de cel mult trei cifre impartite la 20 dau rest 5.Aflati suma acestor numere.

Answer 1

cel mai mic e 100
100:20=5
105:20= 5 r 5
cel mai mare e 999
999:20=49 rest 19
19-5=14
999-14=985
985:20=49 rest 5
deci nr sunt 105,125,145,......,965,985
corespunzator caturilor 5,6,7,....,48,49
deci sunt 49-4=45 nr
suma lor 105+125+145+......+965+985 =........=(105+985) *45/2=1090*45/2=.....