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How many 7-digit numbers that do not start nor end with 1 are there?

 Dec 19, 2019
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The first digit from the left, you have = 8 choices.

 

The 2nd, 3rd, 4th, 5th and 6th from the left, you have =10 x 10 x 10 x 10 x 10 =10^5 choices

 

The 7th and last digit from the left = 9 choices

 

So, the total number of integers =8 x 10^5 x 9 =7,200,000 such numbers.

 Dec 19, 2019

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