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Home Aptitude HCF and LCM Comments

  • Question
  • L.C.M of two prime numbers x and y (x>y) is 161. The value of 3y-x is :


  • Options
  • A. -2
  • B. -1
  • C. 1
  • D. 2

  • Correct Answer
  • -2 

    Explanation

     H. C. F of two prime numbers is 1.  Product of numbers = 1 x 161 = 161.

     Let the numbers be a and b . Then , ab= 161.

     Now, co-primes with  product 161 are (1, 161) and (7, 23).

     Since x and y are prime numbers and x >y , we have x=23 and y=7.

     Therefore,  3y-x = (3 x 7)-23 = -2


  • Search Results


    • 1. The L.C.M of two numbers is 495 and their H.C.F is 5. If the sum of the numbers is 100, then their difference is

    • Options
    • A. 10
    • B. 46
    • C. 70
    • D. 90
    • Discuss
    • 2. Product of two co-prime numbers is 117. Their L.C.M should be

    • Options
    • A. 1
    • B. 117
    • C. Equal to their H.C.F
    • D. cannot be calculated
    • Discuss
    • 3. The L.C.M of 22, 54, 108, 135 and 198 is

    • Options
    • A. 330
    • B. 1980
    • C. 5940
    • D. 11880
    • Discuss
    • 4. A rectangular courtyard 3.78 meters long 5.25 meters wide is to be paved exactly with square tiles, all of the same size. what is the largest size of the tile which could be used for the purpose?

    • Options
    • A. 14 cms
    • B. 21 cms
    • C. 42 cms
    • D. None of these
    • Discuss
    • 5. Convert the 0.0068 in to vulgar fraction:

    • Options
    • A. 7/1250
    • B. 17/2500
    • C. 17/5000
    • D. 7/1750
    • Discuss
    • 6. If the sum of two numbers is 55 and the H.C.F. and L.C.M. of these numbers are 5 and 120 respectively, then the sum of the reciprocals of the numbers is equal to:

    • Options
    • A. 55/601
    • B. 601/55
    • C. 11/120
    • D. 120/11
    • Discuss
    • 7. The H.C.F and L.C.M of two numbers are 11 and 385 respectively. If one number lies between 75 and 125 , then that number is

    • Options
    • A. 77
    • B. 88
    • C. 99
    • D. 110
    • Discuss
    • 8. Three numbers are in the ratio 1 : 2 : 3 and the sum of their cubes is 4500 .The smallest numbers is

    • Options
    • A. 4
    • B. 5
    • C. 6
    • D. 10
    • Discuss
    • 9. H.C.F of 4 x 27 x 3125, 8 x 9 x 25 x 7 and 16 x 81 x 5 x 11 x 49 is

    • Options
    • A. 180
    • B. 360
    • C. 540
    • D. 1260
    • Discuss
    • 10. If HCF of two numbers is 8,which of the following can never be their LCM?

    • Options
    • A. 32
    • B. 48
    • C. 60
    • D. 152
    • Discuss


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