milind1979 wrote:

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Which of the following could be the sum of the reciprocals of two different prime numbers?

A. 7/13

B. 10/12

C. 11/30

D. 23/50

E. 19/77

This question has to be solved by taking on option at a time.

However, we do not need to check all the options here as some can be eliminated by checking the given condition.

We have to find the sum of reciprocals of two different prime numbers.

This means that the denominator will be the multiplication of the two different prime numbers.

Checking the options for this.

Option A = 13*1. Does not satisfy the condition of two prime numbers

Option B = 10/12 = 5/6, Here 6 = 2*3. This is what we need.

To cross check, see that 1/2 + 1/3 = 5/6 = 10/12 Our answer.

Let us check for the others too

Option C: 30 = 5*6 or 3*10. Does not satisfy the condition of two prime numbers

Option D: 50 = 25*2 or 50*1. Does not satisfy the condition of two prime numbers

Option E: 77 = 7*11. This satisfies our condition.

Checking for the numerator: 1/11 + 1/7 = 18/77

But option has 19/77. Hence not the correct answer.

Correct answer: Option B