1.

If G is the intersection of diagonals of a parallelogram ABCD and O is any point, then ` O vecA + O vec B + O vec C + vec (OD) = `A. ` 2 vec(OG)`B. `4 vec(OG)`C. `5 vec (OG)`D. `3 vec (OG)`

Answer» Correct Answer - B
Talking O as the origin, let the position vectors of A, B, C and D be ` vec a , vec b , vec c and vec d ` respectively.
In `Delta` OAC, G is the mid-point of AC.
` O vec A + O vec C = 2 O vec G " " ` (i)
` In `Delta OBD,` G is the mid-point of BC.
` therefore O vec B + O vec D = 2 O vec G " " ` (ii)
Adding (i) and (ii) , we get
`O vec A + O vec B + O vec C + O vec D = 4 O vec G `


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