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The sum of two numbers is 72. Their HCF and LCM are 2 and 102, respectively. The sum of the reciprocals of the same two numbers is:
Question

The sum of two numbers is 72. Their HCF and LCM are 2 and 102, respectively. The sum of the reciprocals of the same two numbers is:

A.

5/17

B.

6/17

C.

7/19

D.

8/19

Correct option is B

Given:
Sum of two numbers = 72
HCF of the two numbers = 2
LCM of the two numbers = 102
Formula Used:
a × b = HCF × LCM
Sum of reciprocals: 1a+1b=a+ba×b \frac{1}{a} + \frac{1}{b} = \frac{a + b}{a \times b}​​
Where a is first number and b is second number. ​
Solution:
Using the formula for the product of two numbers:
a × b = HCF × LCM = 2 × 102 = 204
So, a × b = 204
Now,
a + b = 72
Now, the sum of the reciprocals of the two numbers is:
1a+1b =a+ba×b =72204 =1234 =617\frac{1}{a} + \frac{1}{b} \\ \ \\= \frac{a + b}{a \times b} \\ \ \\= \frac{72}{204}\\ \ \\= \frac{12}{34}\\ \ \\= \frac{6}{17}​​​
Thus, the sum of the reciprocals of the two numbers is 617. \frac{6}{17}.​​

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