Question

s ? t 1 yd u 4 yd

Explanation:

Step1: Apply Pythagorean theorem

In right - triangle $\triangle STU$, by the Pythagorean theorem $a^{2}+b^{2}=c^{2}$, where $c$ is the hypotenuse and $a,b$ are the legs. Here, $c = SU = 4$ yd, $a=TU = 1$ yd, and we want to find $ST$. Let $ST=x$. Then $x^{2}+1^{2}=4^{2}$.

Step2: Solve for $x$

$x^{2}=4^{2}-1^{2}=16 - 1=15$. So $x=\sqrt{15}\text{ yd}$.

Answer:

$\sqrt{15}\text{ yd}$