How many zeros ?

A certain street has 1001 buildings. A sign-maker is contracted to number the houses from 0 to 1000. How many zeroes will he need?


The answer is 193.

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1 solution

Caleb Townsend
Apr 2, 2015

For the one-digit numbers including 0 , 0, There is only one 0 , 0, and that is 0 0 itself.

For the two-digit numbers, only numbers ending in 0 0 are valid; therefore there are nine 0 0 s.

For the three-digit numbers, there are two 0 0 s at every multiple of 100 , 100, one 0 0 at other multiples of 10 , 10, and nine other 0 0 s in the middle digit of the first ten numbers of every hundred. This adds up to twenty 0 0 s per hundred, or 180 180 0 0 s total.

There are three 0 0 s in 1000. 1000.

So the total number of 0 0 s is 1 + 9 + 180 + 3 = 193 1 + 9 + 180 + 3 = \boxed{193}

Yes you are right >>> 1001 buildings >> I modified the text.

Ossama Ismail - 6 years, 2 months ago

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