Answer 1

Perpendicular drawn from the centre of the circle to the chord bisects the chord.

So, PD = `1/2` CD = `48/2` = 24 cm

In Δ OPD, 

We apply the pythagoras theorem, 

OP² + PD² = OD²

⇒ OP² + 24² = 25²

⇒ OP² = 25² - 24² = 625 -576 = 49

⇒ OP² = 49

⇒ OP = 7 CM