CBSE  /  Class 11  /  Maths  /  Sequences and Series

  • 1. 
    If a, b, c are in G.P., then the equations ax² + 2bx + c = 0 and dx² + 2ex + f = 0 have a common root if d/a, e/b, f/c are in

  • AP
  • GP
  • HP
  • none of these

  • 2. 
    If a, b, c are in AP then

  • b = a + c
  • 2b = a + c
  • b² = a + c
  • 2b² = a + c

  • 3. 
    Three numbers form an increasing GP. If the middle term is doubled, then the new numbers are in Ap. The common ratio of GP is

  • 2 + √3
  • 2 – √3
  • 2 ± √3
  • None of these

  • 4. 
    The sum of n terms of the series (1/1.2) + (1/2.3) + (1/3.4) + …… is

  • n/(n+1)
  • 1/(n+1)
  • 1/n
  • None of these

  • 5. 
    If 1/(b + c), 1/(c + a), 1/(a + b) are in AP then

  • a, b, c are in AP
  • a², b², c² are in AP
  • 1/1, 1/b, 1/c are in AP
  • None of these

  • 6. 
    The sum of series 1/2! + 1/4! + 1/6! + ….. is

  • e² - 1 / 2
  • (e - 1)² /2 e
  • e² - 1 / 2 e
  • e² - 2 / e

  • 7. 
    The third term of a geometric progression is 4. The product of the first five terms is

  • 43
  • 45
  • 44
  • none of these

  • 8. 
    Let Tr be the r th term of an A.P., for r = 1, 2, 3, ... If for some positive integers m, n, we have Tm = 1/n and Tn = 1/m, then Tm n equals

  • 1/m n
  • 1/m + 1/n
  • 1
  • 0

  • 9. 
    The sum of two numbers is 13/6 An even number of arithmetic means are being inserted between them and their sum exceeds their number by 1. Then the number of means inserted is

  • 2
  • 4
  • 6
  • 8

  • 10. 
    If the sum of the roots of the quadratic equation ax² + bx + c = 0 is equal to the sum of the squares of their reciprocals, then a/c, b/a, c/b are in

  • A.P.
  • G.P.
  • H.P.
  • A.G.P.
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