Question

The foot of a ladder is 6 m away from its wall and its top reaches a Window 8 m above the ground find the length of ladder

Answer 1

The 'ladder', 'height to which it reaches' and 'foot of ladder from wall' forms a right angled triangle.
ladder = hypotenuse(h)
height to which it reaches = base(b)
foot of ladder from wall = altitude(a)

initially, a = 8m, b = 6m
h² = a² + b²
⇒ h = √(a²+b²) = √(8² + 6²) = √100 = 10m

when foot is 8m away from wall,
b = 8m, h = 10m, a = ?
h² = a² + b²
⇒ a² = h² - b²
⇒ a = √(h² - b²) = √(10² - 8²) = √36 = 6m

So its top reaches 6m height

Answer 2

By Pythagoras' theorem, your answer should be √(6²+8²) = 10 metres.