Question

Quantos números 1 eu tenho de 1 até 191?

Answer 1

De 1 a 10 = 2
11-20=>10
21-30=>1
31-91=>7
100-109=>11
110-120=>22
121-130=>11
131-140=>11
141-150=>11
151-160=>11
161-170=>11
171-180=>11
181-190=>11
191=>2
2+10+1+7+22 +2+11+11+11+11+11+11+11+11=
132

são 132 numeroos

Answer 2

(1,11,21,31, ..........................,191)

an = 191
a1= 1 
n= ?
r = 11-1 = 10

191 = 1 + (n - 1) .10
191-1 = 10n - 10
191-1+10 = 10n
200 = 10n
n = 200/10

n = 20