Let OA= a, OB=12 a+4 b and OC= b, where O is the origin. If S is the parallelogram with adjacent sides OA and OC, then area of the quadrilateral OABCarea of S is equal to .
- 7
- 6
- 8
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Answer
(3) 8
Solution
[figure]
Area of S =| a b|
∵ Diagonal OB splits OABC into OAB and OBC:
Area(OABC) = 12| a (12 a+4 b)|+ 12|(12 a+4 b) b|
= 12(4| a b|)+ 12(12| a b|) ( a a= b b= 0)
=8| a b|
Ratio = 8| a b|| a b|=8
Answer: (3)