What is the length of the diagonal of a cube with a side length of 5 cm? round to the nearest tenth.

If we draw the diagonal we get a right triangle
the legs are 5 and 5 and hyptonuse is the diagonal

remmeber
for a right triangle with legs a and  b and hyptonuse c
a²+b²=c²

so
a=b=5
5²+5²=c²
25+25=c²
50=c²
sqrt both sides
5√2=c

the diagonal is 5√2 cm or about 7.0710678118654752440084436210485cm