If rb = 4 and or = 3, then ob = 5 7 2√3

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

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's