Question 1029343
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How many 3-digit numbers are multiple of 21?
I can solve it by counting there is another way to solve this type of problem 
Thanks
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First such number is  105.
Last  such number is  987.

How many intervals by 21 integer numbers are between these two numbers?
It is

{{{(987-105)/21}}} = 42.

So, there are 42 intervals.
Hence, the number of multiples 21 from 105 to 987 inclusively is 42 + 1 = 43.

<U>Answer</U>. There are 43 multiples of 21 that are 3-digit integers.
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