Justin walked 3 miles north and 6 miles west. starting from the same point, tina walked 2 miles south and 4 miles east. how far apart are justin and tina?

a) about 5.8 miles
b) about 11.2 miles
c) about 23 miles
d) about 19.8 miles

Basically, Justin and Tina's paths form two right-angled triangles whose hypotenuses(?) form a straight line between their end points. Therefore we need to find the two distances from the starting point and add them.
Justin walked 3 miles north and 6 miles west so his distance from the start is the square root of 9+36 or 45. This can be simplified to 3√5. 
Tina walked 2 miles south and 4 miles east so her distance from the starting point is the square root of 4 + 16 or 20. This can be written as 2√5.
If we add these two distances together we get 5√5. Hence, Justin and Tina are 5√5 miles away from each other.