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Home Aptitude Odd Man Out and Series See What Others Are Saying!
  • Question
  • Find the sum of n terms of the given series. 1.2.4 +2.3.5 + 3.4.6 + ...


  • Options
  • A. n(n + 1) (n + 2)
  • B. [n(n + 1) / 12] (3n2 + 19n + 26)
  • C. [(n + 1) (n + 2) (n + 3)] / 4
  • D. (n2(n + 1) (n + 2) (n + 3) / 3

  • Correct Answer
  • [n(n + 1) / 12] (3n2 + 19n + 26) 

    Explanation

    Put n = 1, now the sum of the series = 1.2.4 = 8
    Put n = 1, in the options
    (a) 1(1 + 1) (1 + 2) = 6
    (b) 1(1 + 1)/12 x (3 + 19 + 26) = 8
    (c) (1 + 1) (1 + 2) (1 + 3)/4 = 6
    (d) 1(1 + 1) (1 + 2) (1 + 3 )/3 = 8
    As, the sum of series = 8
    Hence, option (a) and (c) can be rejected.
    Now, put n = 2
    Sum 1. 2. 4 + 2 . 3 . 5 = 38
    Put n = 2, in option (b)
    2(2 + 1)/12 (3 x 4 + 19 x 2 + 26)38
    Hence, (b) is the correct option.


  • More questions

    • 1. 
      Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?

    • Options
    • A. 18 days
    • B. 21 days
    • C. 3 days
    • D. 6 days
    • Discuss
    • 2. 
      750.0003 ÷ 19.999 =?

    • Options
    • A. 49
    • B. 18
    • C. 22
    • D. 38
    • Discuss
    • 3. 
      105, 85, 60, 30, 0, - 45, - 90?

    • Options
    • A. 0
    • B. 85
    • C. -45
    • D. 60
    • Discuss
    • 4. 
      Let A = {1, 2, {3, 4}, 5}. Which of the following statements is true?

    • Options
    • A. {3, 4} ? A
    • B. {3, 4} ? A
    • C. 1 ? A
    • D. {1, 2, 5} ? A
    • Discuss
    • 5. 
      Two vessels A and B contains milk and water mixed in the ratio 5 : 3 and 2 : 3. When these mixtures are mixed to form a new mixture containing half milk and half water, they must be taken in the ratio ?

    • Options
    • A. 2 : 5
    • B. 3 : 5
    • C. 4 : 5
    • D. 7 : 3
    • Discuss
    • 6. 
      1, 2, 4, 8, 16, 32, 64, (...), 256?

    • Options
    • A. 148
    • B. 128
    • C. 154
    • D. 164
    • Discuss
    • 7. 
      A tree is 12 m tall and casts an an 8 m long shadow. At the same time, a flag pole caste a 100 m long shadow. How long is the flag pole?

    • Options
    • A. 150 m
    • B. 200 m
    • C. 125 m
    • D. 115 m
    • Discuss
    • 8. 
      8% of 96 =? of 1/25

    • Options
    • A. 19.2
    • B. 7.68
    • C. 1.92
    • D. None of these
    • Discuss
    • 9. A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?

    • Options
    • A. Rs. 35
    • B. Rs. 245
    • C. Rs. 350
    • D. Cannot be determined
    • E. None of these
    • Discuss
    • 10. 
      If the hands of a clock coincide in every 65 minutes (true time), in 24 hours the clock will gain:

    • Options
    • A. 10 10 minutes. 143
    • B. 9 12 minutes. 143
    • C. 11 12 minutes. 143
    • D. 12 10 minutes. 143
    • Discuss


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