Number System
Aptitude

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Q.

A girl wrote all the numbers from 100 to 200. Then she started counting the number of one's that has been used while writing all these numbers. What is the number that she got?

 A.

111

 B.

119

 C.

120

 D.

121

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Solution:
Option(C) is correct

From 100 to 200 there are 101 numbers.
There are 100, 1's in the hundred place.
10, 1's in tens place and10, 1's in unit place.

Thus, the answer is $100+10+10 =$ 120.

Edit: For the explanation on the number of 1's in hundred, ten and unit's place, check Kapil's comment.


(5) Comment(s)


Deepika Balwa
 ()

but then 111 is counted twice...Why ?


Saiikiran
 ()

It is not a question of how many numbers tat was counted, rather it is how many 1's are counted.. So in 111. We need to count it as 3 ones.

Hope u got it now :)


Manpinder
 ()

Could you please explain this more?

Thank you!!


Kapil
 ()

this type of questions needs calculations based on place i.e.

hundred place, tens place, unit place.

100-200: hundred place = 100.
(100,101,102,103...198,199)

100-200: Tens place = 10.
(110,111,112,113,114....118,119)

100-200: Unit Place = 10.
(101,111,121...181,191)