Answer:
≈
![21.21\ cm](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f81b3mbfqda9azytbcq6r0o1sv5egfblr1.png)
Explanation:
You need to use the Pythagorean Theorem:
![a^2=b^2+c^2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/g7lqyavlhxie81evds9kmmjv6zlmpg9yqr.png)
Where "a" is the hypotenuse and "b" and "c" are the legs of the right triangle.
Since the sheet of paper was an square, then:
![b=15\ cm\\\\c=15\ cm](https://img.qammunity.org/2020/formulas/mathematics/middle-school/892q06dl70oc5uv9esvgedecx81z3v2zju.png)
Knowing this, you can substitute values into
and solve for "a":
![a^2=(15\ cm)^2+(15\ cm)^2\\\\a=√((15cm)^2+(15cm)^2)\\\\a=15√(2)\ cm](https://img.qammunity.org/2020/formulas/mathematics/middle-school/c1snx25oddv8r6hh97o0gyjllhn5gicyeb.png)
≈
![21.21\ cm](https://img.qammunity.org/2020/formulas/mathematics/middle-school/f81b3mbfqda9azytbcq6r0o1sv5egfblr1.png)