Business Mathematics

181. If probability P( n, r) =720 and combination C(n, r) =120 then r is

  1. 9
  2. 8
  3. 5
  4. 3
Correct answer: (D)
3

182. For 1) 2a +c -2d = 5
2) –a +2b +c = 4
3) +b -c +3d = 1
4) 2a -b +2c -5d = 4

  1. Equation 1 is dependent on 3 and 4
  2. Equation 2 is dependent on 3 and 4
  3. Equation 1 is dependent on 2 and 3
  4. None
Correct answer: (A)
Equation 1 is dependent on 3 and 4

183. Is xyz

  1. Non linear
  2. Linear
  3. Binomial
  4. None
Correct answer: (A)
Non linear

184. Inverse of a square matrix A, denoted by A-1 is also a square matrix of the same order such that A A-1 is

  1. A-1
  2. A
  3. I
  4. AI
Correct answer: (C)
I

185. A diagonal matrix in which all diagonal elements are equal is called

  1. Unit matrix
  2. Null matrix
  3. Scalar matrix
  4. Triangular matrix
Correct answer: (C)
Scalar matrix

186. If A, B are symmetric matrices of the same order, then AB – BA is a

  1. Skew symmetric matrix
  2. Symmetric matrix
  3. Zero matrix
  4. Identity matrix
Correct answer: (A)
Skew symmetric matrix

187. If A = a b is such that A2 = I, then c - a

  1. 1+ a2 + bc =0
  2. 1 –a2 + bc =0
  3. 1 –a2 -bc = 0
  4. 1 +a2 -bc=0
Correct answer: (B)

1 –a2 -bc = 0

188. Let A be a square matrix of order 3 x 3, then | kA | is equal to

  1. k | A |
  2. k2 | A |
  3. k3 | A |
  4. 3k | A |
Correct answer: (C)

k3 | A |

189. Equation of line joining (1,2) and (3,6) using determinants is

  1. y = 3x
  2. y =2x
  3. x = 2y
  4. x =3x
Correct answer: (B)
y =2x

190. If A is an invertible matrix of order 2, then det( A-1) is equal to

  1. det( A)
  2. 1/det( A)
  3. 1
  4. 0
Correct answer: (B)
1/det( A)
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