Since the North and the East directions are perpendicular
Then we will have a right triangle has two legs, North and east
Its hypotenuse is the straight distance between the 2 houses
By using the Pythagoras Theorem
![\text{leg}1^2+leg2^2=hypotenuse^2](https://img.qammunity.org/2023/formulas/mathematics/college/71135bgyt9ny7g189itlw4085nf4wut9qz.png)
Since leg1 = 12 km
Since leg2 = 16 km
Substitute them in the rule above
![\begin{gathered} 12^2+16^2=hyp.^2 \\ 144+256=hyp.^2 \\ 400=hyp.^2 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zkla47ic9m6oydyw18arm3uds0thuli37l.png)
Take square root for both sides
![20=\text{hypo.}](https://img.qammunity.org/2023/formulas/mathematics/college/14esv4spwxzddmjy3kchg8a7mvp592h9v6.png)
The distance between the parents' and grandparents" houses is 20 KM