Question

If RB = 4 and OR = 3, then OB = 5 7 2√3

Answer 1

The complete question in the attached figure

we know that

triangle OBR is a right triangle
so
applying the Pythagorean theorem

OB²=OR²+RB²----> OB²=3²+4²-----> 25
OB=√25-----> OB=5 units

the answer is
OB=5 units

Answer 2

Answer:

OB = 5 units

Step-by-step explanation:

OPtion I is right

Given in the picture is a circle.

AB is a chord, O is the centre of the circle

OR is drawn perpendicular to AB.

Given that OR =3, and RB =4

Since ORB is a right triangle with known legs we can find the hypotenuse OB using Pythagorean theorem

$OB^2=OR^2+RB^2=3^2+4^2 =25\\OB =5$

Hence radius of the circle = 5 units.