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LCM & HCF Test 453
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LCM & HCF Test 453
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  • Question 1/10
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    Find the smallest number which should be added to the smallest number divisible by 6, 9 and 15 to make it a perfect square.
    Solutions

    6 = 2 × 3

    9 = 32

    15 = 3 × 5

    LCM of 6 ,9 and 15 = 2 × 32 × 5 = 90

    Perfect square number greater than 90 is 100

    Required number = 100 – 90 = 10

  • Question 2/10
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    The ratio of two numbers is 5 : 4 and their HCF is 4 . What is their LCM?
    Solutions

    Let the numbers be 5x and 4x

    HCF of 5x and 4x = x = 4

    Numbers are (5 × 4),(4 × 4) = 20, 16

    20 = 5 × 4

    16 = 4 × 4

    LCM of 20 and 16 = 5 × 4 × 4 = 80

  • Question 3/10
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    What will be the least number which when doubled will be exactly divisible by 15, 18, 25 and 32?
    Solutions

    15 = 3 × 5

    18 = 2 × 32

    25 = 52

    32 = 25

    LCM of 15, 18 , 25 and 32 =  25 × 32 × 52 = 7200

    Required number =  = 3600

    "Hence, option A is the correct answer."

  • Question 4/10
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    The HCF of two numbers 2040 and 391 is:
    Solutions
     2040 = 17 × 120

    391 = 17 × 23

    HCF of 2040 and 391 is 17

    Hence, option D is the correct answer.

  • Question 5/10
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    Two numbers are in the ratio of 6 : 5. If their HCF is 3, then what is the LCM of the two numbers?
    Solutions
     Ratio of two numbers = 6 : 5

    HCF of two numbers = 3

    LCM of the numbers = 6 × 5 × 3 = 90

  • Question 6/10
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    How many distinct natural numbers are the divisors of (30)4?
    Solutions

    (30)4 = 24 × 34 × 54

    Divisors that are distinct natural numbers

    = (4 + 1) × (4 + 1) × (4 + 1) = 5 × 5 × 5 = 125

  • Question 7/10
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    Three milk containers A, B and C contain milk 637 liters ,707 liters and 1523 liters respectively. Ram takes 8 liters from container A, 4 liters from container B and average of taken milk from container A and B taken from container C. Remaining liters of milk packed into bottles having equal volume. Find total number of bottles that are needed to pack the milk?
    Solutions

    According to question, milk in containers A, B and C are 637liters, 707 liters and 1523 liters respectively

    Taken milk by ram from container A = 8 liters

    Taken milk by ram from container B = 4 liters

    Taken milk by ram from container C = average of A and B =  = 6 liters

    Remaining milk in container A = 637 – 8 = 629 liters

    Remaining milk in container B = 707 – 4 = 703 liters

    Remaining milk in container C = 1523 – 6 = 1517 liters

    For equal volume HCF of 629, 703 and 1517 = 37

    Now, required bottle for container A = = 17

    Required bottle for container B =  = 19

    Required bottle for container C = = 41

    Therefore, required total number of bottles = 17 + 19 + 41 = 77

  • Question 8/10
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    Which of the following is the smallest number that is a perfect square and is divisible by each of the numbers 6, 8 and 15?
    Solutions

    Smallest number that is divisible by each of the numbers 6, 8 and 15 is LCM of 6, 8 and 15, i.e., 120.

    Thus the number is of form 120k where k is a natural number.

    Among the given options only 3600 is divisible by 120.

    So, the required number is 3600.

    Hence, the correct answer is option D.

  • Question 9/10
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    The HCF and LCM. of two numbers are 286 and 1716 respectively. If the ratio between the two numbers is 2 : 3, then the greater of the two numbers is
    Solutions

    Let the numbers be 2x and 3x.

    Concept:

    Multiplication of two numbers = Multiplication of their LCM and HCF

    (2x) × (3x) = 286 × 1716

    6x2 = 286 × 1716

    x2 =

    x2 = 286 × 286

    x = 286

    Therefore, the greater number is 286 × 3 = 858

  • Question 10/10
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    The ratio of two numbers is 9 : 17 and their HCF is 13 . Their LCM is:
    Solutions

    Since absolute ratio of the numbers and HCF of the numbers are given, the numbers are 9 × 13 = 117 and 17 × 13 = 221.

    Now, LCM of 117 and 221 = 117 × 17 = 1989

    Alternate:

    Since absolute ratio of the numbers and HCF of the numbers are given, the LCM of the numbers is 9 × 17 × 13 = 1989

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