Problem Solving

Beth received 3/10 of the votes cast in a certain election. What fraction of the other votes cast would she have needed in order to have received 1/2 of the votes cast?
(A) 1/5
(B) 2/7
(C) 3/10
(D) 7/20
(E) 1/2

Isn't that answer should be 1/5? Can some one please explain how answer could be 2/7?

Beth received 3/10 of the votes cast in a certain election. What fraction of the other votes cast would she have needed in order to have received 1/2 of the votes cast?
(A) 1/5
(B) 2/7
(C) 3/10
(D) 7/20
(E) 1/2

Discussed in an earlier thread...however, here it goes

If total votes cast were x. Beth received 3x/10
Beth needs 2x/10 more votes to have 5x/10 or 1/2 of the total number of votes
Remaining votes = x-3x/10 = 7x/10
So fraction = (2x/10)/(7x/10)
=2/7
Hence B

wow Cybermusings
this is a good one!

What am I doing wrong here:

beth received 3/10 votes remaining 1- (3/10) = 7/10.

let x be the required fraction to make it 1/2

so 7/10 - x = 1/2

so x = 7/10 -1/2 = 1/5

my answer is 1/5

to verify if we add votes received by beth 3/10 + 1/5 = 1/2