ABC is a triangle, right-angled at C. If AB = 25 cm and AC = 7 cm, find BC.
It is given in the question that,
AB = 25 cm
Also,
AC = 7 cm
We have to find BC
We know that,
According to Pythagoras theorem,
In a right angled triangle:
(Hypotenuse)2 = (Perpendicular)2 + (Base)2
By applying Pythagoras theorem in 
ABC, we get:
(AB)2 = (AC)2 + (BC)2
(BC)2 = (AB)2 - (AC)2
(BC)2 = (25)2 – (7)2
(BC)2 = 625 – 49
(BC)2 = 576
Hence,
QR = 
QR = 24 cm
2