Question

above what value of inside diameter will 10% of the piston rings fall?

Answer 1

$X\sim N(10, (0.03)^2)$

$$P(X>x)=1-P(Z\le\dfrac{x-10}{0.03})=0.1$$

$$P(Z\le\dfrac{x-10}{0.03})=0.9$$

$$\dfrac{x-10}{0.03}=1.28155$$

$$x=10+0.03(1.28155)$$

$$x=10.0384\ cm$$