Answer:the length of OB is 10 cm
Step-by-step explanation:
The given figure is a rectangle. In a rectangle, the opposite sides are equal. The diagonals of the rectangle are equal and they bisect each other at the midpoint of the rectangle. This means that BO = DO and AO = CO.
BD = OB + DO
And OB = BD/2
Since BD = 20 cm
OB = 20/2 = 10 cm
