Question

How many times does the digit $1$ appear in numbers from $1$ to $100$?

• A. $18$
• B. $19$
• C. $20$
• D. $21$

Answer 1

The correct option is D $21$

$\Rightarrow$ 1–10 = 2 times

$\Rightarrow$ 11–20 = 10 times

$\Rightarrow$ 21–30 = 1 time

$\Rightarrow$ 31–40 = 1 time

$\Rightarrow$ 41–50 = 1 time

$\Rightarrow$ 51–60 = 1 time

$\Rightarrow$ 61–70 = 1 time

$\Rightarrow$ 71–80 = 1 time

$\Rightarrow$ 81–90 = 1 time

$\Rightarrow$ 91–100 = 2 times

$\Rightarrow$ $Total=2+10+1+1+1+1+1+1+1+2=21$

$\therefore$ The digit 1 appear in number from 1 to 100 is $21$.