IMO - A

In a certain city, the ratio of the number of people who purchase newspaper X to the number of people who purchase newspaper Y is 7:1. What percent of the population purchases newspaper Y ?
(1) Twenty-seven percent of the population purchases neither newspaper X nor newspaper Y .
(2) Seventy percent of the people who purchase newspaper Y also purchase newspaper X .

Venn diagram . Two circle X and Y intersect.
(1) Tell us that 73% buy either X and Y or both (X and Y intersection).
the ratio of X : Y is 7:1 so if total pop. is 100 X = 70 & Y = 10 but intersection of X and Y is not known
(2) Tells us the people who buy both the newspapers = 7
But without (1) it is not possible to know the percentage of pop.

(1) and (2) X^Y = 7 so those who just X = 63 and just Y = 3 that is 73 who buy newspapers
IMO C

gmatassistance wrote:In a certain city, the ratio of the number of people who purchase newspaper X to the number of people who purchase newspaper Y is 7:1. What percent of the population purchases newspaper Y ?

(1) Twenty-seven percent of the population purchases neither newspaper X nor newspaper Y .

(2) Seventy percent of the people who purchase newspaper Y also purchase newspaper X .

IMO C. kstv's explanation is gud enough