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Home Aptitude Simplification See What Others Are Saying!
  • Question
  • 1/(1 x 4) + 1/(4 x 7) + 1/(7 x 10) + 1/(10 x 13) + 1/(13 x 16) =?


  • Options
  • A. 5/16
  • B. 3/16
  • C. 7/16
  • D. 11/16

  • Correct Answer
  • 5/16 

    Explanation

    Given expression can be written as
    = 1/(1 x 4) + 1/(4 x 7) + 1/(7 x 10) + 1/(10 x 13) + 1/(13 x 16)
    = 1/3{ 3/(1 x 4) + 3/(4 x 7) + 3/(7 x 10) + 3/(10 x 13) + 3/(13 x 16) }
    = 1/3{ (4 - 1)/(1 x 4) + (7 - 4)/(4 x 7) + (10 - 7 )/(7 x 10) + (13 - 10)/(10 x 13) + (16 - 13/(13 x 16) }
    = 1/3[(1 - 1/4) + (1/4 - 1/7) + (1/7 - 1/10) + (1/10 - 1/13) + (1/13 - 1/16)]
    = 1/3[1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + 1/13 - 1/16]
    = 1/3[1 - 1/16]
    = 1/3[ (16 - 1)/16]
    = 1/3[ (15)/16]
    = 1 x 15/ 3 x 16
    = 5/16


  • More questions

    • 1. 
      A and B together can complete a work in 3 days. They started together but after 2 days, B left the work. If the work is completed after 2 more days, B alone could do the work in how many days?

    • Options
    • A. 5
    • B. 6
    • C. 7
    • D. 10
    • Discuss
    • 2. 
      A wheel makes 1000 revolutions in covering a distance of 88 km. the diameter of the wheel is?

    • Options
    • A. 24 meters
    • B. 40 meters
    • C. 28 meters
    • D. 14 meters
    • Discuss
    • 3. 25, 36, 49, 81, 121, 169, 225

    • Options
    • A. 36
    • B. 49
    • C. 121
    • D. 169
    • Discuss
    • 4. 
      (.896 x .752 +.896 x .248) / (.7 x .034 + .7 x.966) =?

    • Options
    • A. 1.28
    • B. 0.976
    • C. 12.8
    • D. 9.76
    • Discuss
    • 5. 
      Einstein goes from Ahmedabad To Lucknow at the speed of 40 km/hr and returned at the speed of 60 km/hr .the average speed of Einstein during the whole journey is

    • Options
    • A. 48 km/hr
    • B. 24 km/hr
    • C. 50 km/hr
    • D. none of these
    • Discuss
    • 6. 
      Today is Monday. After 61 days, it will be

    • Options
    • A. Wednesday
    • B. Saturday
    • C. Tuesday
    • D. Thursday
    • Discuss
    • 7. 9548 + 7314 = 8362 + (?)

    • Options
    • A. 8230
    • B. 8410
    • C. 8500
    • D. 8600
    • E. None of these
    • Discuss
    • 8. 
      The true discount on a certain sum due 1 yr hence at 30% per annum, is ? 240. What is the banker' discount on the same sum for the same time and at the same rate?

    • Options
    • A. ? 400
    • B. ? 212
    • C. ? 312
    • D. ? 445
    • Discuss
    • 9. 
      Calendar of month July is same as that of which month of previous year.

    • Options
    • A. May
    • B. September
    • C. April
    • D. None of these
    • Discuss
    • 10. 
      A coin is successively tossed two times. Find the probability of getting? (1) exactly one head (2)at least one head

    • Options
    • A. 1/2 , 3/4
    • B. 2/3, 1/4
    • C. 1/4, 4/5
    • D. 1/2, 2/3
    • Discuss


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