- Thread starter Tsrnc2
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How many 4-digit numbers are there with all four numbers same (e.g. 1111 or 7777, etc.)?

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We cannot have \(\displaystyle (XXXX)\) where \(\displaystyle X\) is digit.

Let's see, we cannot have \(\displaystyle (19XY)\) where \(\displaystyle X~\&~Y\) are digits.

Now we need to double that number.

How many increasing strings of four are there? Did you include \(\displaystyle \large\bf 0123~?\)

Now we need to double that number.