
The LCM and HCF of two rational numbers are equal. Then the numbers are?
A) prime
B) co-prime
C) composite
D) equal
Answer
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Hint: The HCF of two numbers is always a factor of both the numbers. There is a relation between two numbers and their LCM and HCF. Using this, we can find the relation between the numbers.
Formula used: Product of two numbers is equal to the product of their Least common divisor(LCM) and Highest common factor(HCF)
where and are any two numbers.
is the Least Common Multiple
is the Highest Common Factor
Complete step-by-step answer:
Given data
LCM and HCF of two numbers are the same.
Let the two rational numbers be and .
Given that
Let, , for some value .
HCF being the highest common factor is always a factor of both the numbers.
Therefore the numbers can be written as multiples of HCF.
That is,
, for some natural number
, for some natural number
Now, since the product of two numbers is equal to the product of their LCM and HCF, we have
Substituting the values for , , their LCM and HCF,
Cancelling from both sides,
( since and are natural numbers).
Substituting these we get and as
Therefore, the two numbers are the equal.
So, the correct answer is “Option D”.
Additional Information: HCF of two numbers is always less than or equal to their LCM. Also LCM is always a multiple of HCF.
Note: Two numbers are said to be co-prime when their HCF is . Prime numbers are those numbers with only factors and the number itself. The numbers which are not prime are called composite numbers. Highest common factor (HCF) is also known as the greatest common divisor.
Formula used: Product of two numbers is equal to the product of their Least common divisor(LCM) and Highest common factor(HCF)
where
Complete step-by-step answer:
Given data
LCM and HCF of two numbers are the same.
Let the two rational numbers be
Given that
Let,
HCF being the highest common factor is always a factor of both the numbers.
Therefore the numbers can be written as multiples of HCF.
That is,
Now, since the product of two numbers is equal to the product of their LCM and HCF, we have
Substituting the values for
Cancelling
Substituting these we get
Therefore, the two numbers are the equal.
So, the correct answer is “Option D”.
Additional Information: HCF of two numbers is always less than or equal to their LCM. Also LCM is always a multiple of HCF.
Note: Two numbers are said to be co-prime when their HCF is
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