Why do we divide by uncertainty value to get the minimum possible outcome?

Question

I’ll explain it with an example, say there is a cylinder whose diameter is known with a +/- 5 percent uncertainty, so this means the actual value could be at maximum 5% higher than the nominal value and the min 5% lower. What I’ve seen in a textbook is that in order to get the minimum possible value, they divided the nominal value (let’s call it d) by 1+ 5 percent : min=d/1.05

Why can’t they just multiply the nominal value by 0.95 just like how we multiply d by 1.05 to get the max value?

In: 2

Answer 1

it’s because the 5% and be plus or minus depending on the overall test value. The 0.95 would not be a accurate due to what’s called mathematical lean. Wiki will explain more it’s hard to totally explain in a post.