Sunday, April 29, 2007

ALGEBRA QUESTION OF THE DAY

If p and q are different prime numbers and pq/2 is also a prime number, then p + q is
(A) an odd number
(B) an even number
(C) a prime number
(D) a negative number
(E) not a prime number

7 comments:

Madhur said...

E

Anonymous said...

e

Madhur said...

i think E is wrong
what if p=2 and q=3

pq/2 =3
p+q=5 … a prime number

i prefer A,
since pq/2 s prime refers either p or q is 2.
then p+q=2+q
where q is odd.

so asum will be always odd.

what is the answer?

Unknown said...

Answer is A

Bindu said...
This comment has been removed by the author.
Nags said...

madhur is right.
A

Admin said...

Since pq/2 is prime, it is an integer. Hence, either p or q must be even; otherwise, the 2 would not
cancel and pq/2 would be a fraction. The only even prime number is 2. Hence, either p or q, but not both,
must be 2. The other one is an odd prime number. Now, the sum of an even number and an odd number is
an odd number. The answer is (A).