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  • 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. 
      If a : b = 2 : 3 and 2 : a =1 : 2, then the value of 'b' is?

    • Options
    • A. 4
    • B. 6
    • C. 1 / 3
    • D. 3 / 2
    • Discuss
    • 2. 
      0.6 of a number equals 0.09 of another number. The ratio of the number is?

    • Options
    • A. 2 : 3
    • B. 1 : 15
    • C. 20 : 3
    • D. 3 : 20
    • Discuss
    • 3. 
      If a/3 = b/8, then ( a + 3 ) : ( b + 8 ) is equal to?

    • Options
    • A. 3 : 8
    • B. 8 : 3
    • C. 5 : 8
    • D. 3 : 5
    • Discuss
    • 4. 
      4, 19, 49,?, 229

    • Options
    • A. 75
    • B. 109
    • C. 65
    • D. 169
    • Discuss
    • 5. 
      777777 / 11 =?

    • Options
    • A. 7077
    • B. 70707
    • C. 7707
    • D. 7007
    • Discuss
    • 6. 
      Find the cardinal number of the following set {x: x is a natural number ? 30 and is divisible by 7 or 11}

    • Options
    • A. 4
    • B. 8
    • C. 6
    • D. 2
    • Discuss
    • 7. 
      SBI lent ? 1331 lakh to the TATA group at compound interest and got ?1728 lakh after 3 yr. What is the rate of interest charged, if compounded annually?

    • Options
    • A. 11%
    • B. 9.09%
    • C. 12%
    • D. 8.33%
    • Discuss
    • 8. 
      The sum of two numbers is 10. Their product is 20. Find the sum of the reciprocals of the two numbers.

    • Options
    • A. 1
    • B. 3/5
    • C. 1/2
    • D. 11//6
    • Discuss
    • 9. 
      5 men and 6 women can earn ? 2160 in 4 days. 8 men and 10 women can earn ? 4400 in 5 days. In how many days can 4 men and 9 women earn ? 1800?

    • Options
    • A. 3
    • B. 4
    • C. 5
    • D. 6
    • Discuss
    • 10. 
      A train 110 metres long travels at 60 km/hr. How long does it take to cross a telegraph post?

    • Options
    • A. 5 sec.
    • B. 5.6 sec
    • C. 6.6 sec
    • D. 6.8 sec
    • Discuss


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