In the right-angled triangle, what is the length of side BC?

The correct answer is Option (3) → 5 cm

The right angle is at A, so BC, the side opposite it, is the hypotenuse. By the Pythagoras theorem, \(BC^2=AB^2+AC^2\).

• Adding the squares of the two shorter sides: \(BC^2=4^2+3^2=25\)

• So the hypotenuse \(BC=5\) cm

Tip: 3, 4, 5 is the smallest Pythagorean triple; its multiples (6, 8, 10 and 9, 12, 15) turn up often and can be spotted at once.