Difference between revisions of "2021 AMC 10B Problems/Problem 1"
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+ | ==Solution 3== | ||
+ | <math>|x|<3\pi</math> <math>\iff</math> <math>-3\pi<x<3\pi</math>. Since <math>\pi</math> is approximately <math>3.14</math>, <math>3\pi</math> is approximately <math>9.42</math>. We are trying to solve for <math>-9.42<x<9.42</math>, where <math>x\in\mathbb{Z}</math>. Hence, <math>-9.42<x<9.42</math> <math>\implies</math> <math>-9\leq x\leq9</math>, for <math>x\in\mathbb{Z}</math>. The number of integer values of <math>x</math> is <math>9-(-9)+1=19</math>. Therefore, the answer is <math>\boxed{\textbf{(D)}19}</math>. | ||
+ | <br><br> | ||
+ | ~ {TSun} ~ |
Revision as of 18:45, 11 February 2021
Contents
[hide]Problem
How many integer values of satisfy
?
Solution
Since is about
, we multiply 9 by 2 and add 1 to get
~smarty101
Solution 2
There are two cases here.
When and
So then
When and
So then
. Dividing by
and flipping the sign, we get
From case 1 and 2, we need . Since
is an integer, we must have
between
and
. There are a total of
-PureSwag
Solution 3
. Since
is approximately
,
is approximately
. We are trying to solve for
, where
. Hence,
, for
. The number of integer values of
is
. Therefore, the answer is
.
~ {TSun} ~