Question 1176355
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We're told that "if you count by l0s you say its name", which means that the number must end with a 0. 
Counting by 10s is where we start at 10 and increase by 10 each time: 10,20,30,40,50,...
If a number is a multiple of 10, then it ends with a 0.
This is another way of saying 10 is a factor of the mystery number.


The clue that "it can be divided evenly by 3 and 9" means 3 and 9 are factors of this mystery number.


Because 9 and 10 are factors, this makes 9*10 = 90 a factor of the number.


Let's count by 90
90, 180, <font color=red>270</font>, 360, ...
The red value <font color=red>270</font> fits the criteria that we're between 195 and 300. So we stop here because we found the answer.


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Or we could look at it like this:
90x = mystery number, since 90 is a factor
x = some positive whole number


195 < 90x < 300
195/90 < 90x/90 < 300/90 ......... divide all parts by 90
2.167 < x < 3.333
because x is a positive whole number, we can see that only x = 3 works in 2.167 < x < 3.333
In other words, 2.167 < x < 3.333 becomes 2.167 < 3 < 3.333 which is true.


Since x = 3, we know the mystery number is 90x = 90*3 = <font color=red>270</font>


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Answer: <font color=red>270</font>
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