X plus minus 10 percent.

Question

I have $x = 100$. I need to get a range that is plus/minus $10\%$ of $100$.

That means in my case $x=100$:

• $10\%$ of $100$ = $10$
• $100 - 10 = 90$
• $100 + 10 = 110$

That means my range of $100 \pm 10\%$ is: $90 - 110$

Correct?

Answer 1

Yes, that is correct............

Answer 2

Yes it is correct. Do you want a curious fact? You have $100$, you add $10\%$ and you have $110$. Then you take away $10\%$ (that now is worth $11$) and you end up with $99\%$. After adding and afterwards deducting the same $10\%$, you lose $1\%$.

Bad luck? Let's try reversing the process. Start again with $100$ but this time start subtracting $10\%$, so you have $90$. Now add $10\%$ of that and you have... $99$ again!