Answer: 35% least watched both.

Explanation:

As per my understandings, I used matrix to find required percentage. If 60% matched X, then 40% not watched X. Same, if 75% watched Y, then 25% not watched Y. Everybody watched either X or Y, then just put 0 in No-X and No-Y box and balance rest boxes, you will get 35 as minimum people who watched both X or Y.

Please let me know, if I'm wrong.

sushbis wrote:If 60% of a set of people watched a movie X and 75% watched a movie Y and among them they watched only these two movies, then what is the least number of people who watched both?

The question asks for least number of people who watched both, not the least percent of people who watched both.

As percent, n (X & Y) = n (X) + n (Y) - n (X or Y) = 60 + 75 - 100 = 35

Then, look for the least positive integer that could represent 35 percent of some number, and 7 is the best answer, which represents 35 percent of 20.

My answer is [spoiler]7[/spoiler].

Good reply. Kudos!