

To solve these type of problems you need to use the pythagoras theorem ⇨ Hypotenuse² = Base² + Altitude².
Here,
- Altitude = 21 km.
- Base = 20 km
- Hypotenuse = c.
Now, let's solve for c.
Hypotenuse² = Base² + Altitude²
c² = (20)² + (21)²
c² = 400 + 441
c² = 841
c = √841
c = 29.
So, the value of c is 29 km.
NOTE :-
- Pythagoras theorem can be used only in the cases of right-angled triangles. Here, it's given that the triangle is right angled so we can use this theorem.