281. The probability of a bomb hitting a bridge is ½ and two direct hits are needed to destroy it. The least number of bombs required so that the probability of the bridge being destroyed is greater than 0.9 is
8
9
10
11
Correct answer: (B) 9
282. Find the number of non-congruent rectangles that can be found on a normal 8*8 chessboard
24
36
48
None of these
Correct answer: (B) 36
283. Solve -x +2y -3z = 2
-2y = 3
2x -y +z = 9
x =5/2, y =7/2, z=-7/2
x=-3/2, y=-11/2, z=-7/2
x=11/2, y=-3/2, z=-7/2
x=-7/2, y= -3/2, z=-11/2
Correct answer: (C) x=11/2, y=-3/2, z=-7/2
284. Is (x+y)(x-y) = -7
Linear
Non linear
Monomial
None
Correct answer: (B) Non linear
285. The number of non zero rows of a matrix in its row echelon form is a
Row matrix
Column matrix
Rank of matrix
Augmented matrix
Correct answer: (C) Rank of matrix
286. A square matrix with each of its diagonal elements equal to unity and all non diagonal elements equal to zero is
Scalar matrix
Null matrix
Identity matrix
Column matrix
Correct answer: (C) Identity matrix
287. Find the transpose of A= 1 -1
2 3
2 3
1 -1
1 2
-1 3
3 2
1 -1
3 1
2 -1
Correct answer: (B) 1 2
-1 3
288. Which of the following is correct:
Determinant is a square matrix
Determinant is a number associated to a square matrix.
Determinant is a number associated to a matrix.
None of these.
Correct answer: (B) Determinant is a number associated to a square matrix.
289. Find values of k if area of triangle is 3sq. units and vertices are (1,3), (0,0) and (k,0)
+3
-3
± 1
±2
Correct answer: (D) ±2
290. Let A be a non singular matrix of order 3 x3.Then |adj A | is equal to