How many times does the number 1 appear from 1 to 8101?

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CBSE

Mathematics

Grade 7

Number System

Question

Answers

Related Questions

How many times does the digit 1 appear in numbers from 1

to 100

?

A. 18

B. 19

C. 20

D. 21

Answer

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Hint: We will count the digit 1 in a range of 10 numbers like from 1-10, 11-20, and so on.

Here, in the number 11, 1 appears twice and in the range 11-20 it will appear many times.

At last, we will add the times and we will get the final answer.

Complete step-by-step solution:

We have to find the number of times the digit 1 appears in numbers from 1

to 100

.

From 1

to 10

, 1 the digit 1 appears two times for 1 and 10.

From 11

to 20

, 1 the digit 1 appears in 11, 12, 13, 14, 15, 16, 17, 18, 19 and in 11 it appears twice. So, it appears ten times.

From 21

to 30

, 1 the digit 1 appears only once for 21.

From 31

to 40

, 1 the digit 1 appears only once for 31.

From 41

to 50

, 1 the digit 1 appears only once for 41.

From 51

to 60

, 1 the digit 1 appears only once for 51.

From 61

to 70

, 1 the digit 1 appears only once for 61.

From 71

to 80

, 1 the digit 1 appears only once for 71.

From 81

to 90

, 1 the digit 1 appears only once for 81.

From 91

to 100

, 1 the digit 1 appears two times for 91 and 100.

So, the total number of times of repetition of 1 is 2+10+1+1+1+1+1+1+1+2=21

Hence, the digit 1 appears in numbers from 1

to 100

for 21 times.

Hence, the correct answer is D.

c

step-by-step explanation: