Given:

A(1, -2) and B(2, 5) are two points.

OC = 2OA …(i)

and OD = 2OB …(ii)

Adding (i) and (ii), we get

OC + OD = 2OA + 2OB

⇒ CD = 2[OA + OB]

⇒ CD = 2[AB] …(iii)

Now, we find the distance between A and B

d(A,B) = √(x₂ – x₁)² + (y₂ – y₁)²

= √(2 – 1)² + {5 – (-2)}²

= √(1)² + (5 + 2)²

= √1 + 49

= √50

= 5√2

Putting the value in eq. (iii), we get

CD = 2 × 5√2

= 10√2