1
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

If $$a = 2\widehat i + 3\widehat j - \widehat k,b = \widehat i + 2\widehat j - 5\widehat k,c = 3\widehat i + 5\widehat j - \widehat k$$, then a vector perpendicular to a and in the plane containing b and c is

A
$$17\widehat i + 21\widehat j - 123\widehat k$$
B
$$ - 17\widehat i + 21\widehat j - 97\widehat k$$
C
$$ - 17\widehat i - 21\widehat j - 97\widehat k$$
D
$$ - 17\widehat i - 21\widehat j + 97\widehat k$$
2
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

OA and BO are two vectors of magnitudes 5 and 6 respectively. If $$\angle BOA=60^\circ$$, then OA . OB is equal to

A
15
B
0
C
15$$\sqrt3$$
D
$$-15$$
3
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

A vector perpendicular to the plane containing the points $$A(1, - 1,2),B(2,0, - 1),C(0,2,1)$$ is

A
$$8\widehat i + 4\widehat j + 4\widehat k$$
B
$$4\widehat i + 8\widehat j - 4\widehat k$$
C
$$\widehat i + \widehat j - \widehat k$$
D
$$3\widehat i + \widehat j + 2\widehat k$$
4
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

$${1 \over {2\,.\,5}} + {1 \over {5\,.\,8}} + {1 \over {8\,.\,11}} + ............. + {1 \over {(3n - 1)(3n + 2)}} = $$

A
$${n \over {6n + 3}}$$
B
$${n \over {6n - 4}}$$
C
$${{n + 1} \over {6n + 4}}$$
D
$${n \over {6n + 4}}$$
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