If the sum of two co-prime numbers is 11 and their LCM is 30. Find the lower number among the two.
Answer
Correct Answer : a ) 5
Explanation :It is given that,
two numbers are co-prime, which means their HCF is 1 since they don't have any common factor apart from 1.
LCM of the numbers = 30
Let the numbers be x and y
Sum of the numbers = x + y = 11
We know that,
For two numbers
HCF x LCM = product of numbers
1 x 30 = xy
xy = 30 .........(1)
x + y = 11 ...............(2)
Substitute y = 30/x from eq. 1 in eq. 2
x + 30/x = 11
x2 + 30 = 11x
x2 - 11x + 30 = 0
x2 - 6x - 5x + 30 = 0
x(x - 6) - 5(x - 6) = 0
(x - 5)(x - 6) = 0
x = 5, x = 6
If x = 5, y = 6
If x = 6, y = 5
Therefore, the lower among x and y is 5.
Hence, (a) is the correct answer.
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