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Quick question about floor and ceiling when dividing in an inequality
By SuperSheep, history, 7 weeks ago, In English

I'm aware that if $$$2x \leq y$$$ then $$$x \leq \lfloor y/2 \rfloor$$$, and that if $$$2x \geq y$$$ then $$$x \geq \lceil y/2 \rceil$$$

I usually remember that by writing examples like $$$x \in$$$ {$$$2,3$$$}, $$$y=5$$$. But I don't quite get the logic behind that and I'm not sure if it's a general rule that $$$kx \leq y \rightarrow x \leq \lfloor y/k \rfloor$$$.

Any help with understanding that or resources to read about it would be greatly appreciated. Thanks!

 
 
 
 
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7 weeks ago, # |
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Auto comment: topic has been updated by SuperSheep (previous revision, new revision, compare).

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7 weeks ago, # |
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Just read the definition of ceil and floor.

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7 weeks ago, # |
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it's just simple math, im assuming all the variables here are int, therefore automatically rounded down, when you divide a by b, and a % b != 0, the result gets rounded down to the integer part

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7 weeks ago, # |
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If $$$kx\leq y$$$, then $$$x\leq\frac yk$$$. By the definition of floor, the largest integer less than or equal to $$$\frac yk$$$ is $$$\left\lfloor\frac yk\right\rfloor$$$ so if $$$x$$$ is also an integer then $$$x\leq\left\lfloor\frac yk\right\rfloor$$$.

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