All of the Integers from $1$ to $199$, how many times is $1$" used?"


Given: Numbers from $1$ to $199$.

To do: To find that how many times $1$ is used from $1$ to $199$.

Solution:

From $1$ to $99$:

$1,\ 11,\ 21,\ 31,\ 41,\ 51,\ 61,\ 71,\ 81,\ 91$   $1$ is used $10$ times in unit digit

$10,\ 11,\ 12,\ 13,\ 14,\ 15,\ 16,\ 17,\ 18,\ 19$    $1$ is used $10$ times in ten's Digit

Therefore, from $1$ to $99$, $1$ is used $10+10=20$ times.

And this will repeat from $100$ to $199$ too,

Therefore,   $1$ is used $20$ times in units & tens Digit place

$1$ will be used $20+20=40$ times.

$1$ will be $100$ times at $100$ place

Hence, In writhing all of the integers from $1$ to $199$, $1$ is used$=100+40=140$ times

Updated on: 10-Oct-2022

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