The following information is also given with the question.

In a marketing survey for products A, B, and C, 1,000 people were asked which of the products, if any, they use. The three circular regions in the diagram above represent the numbers of people who use products A, B,
and C, according to the survey results. Of the people surveyed, a total of 400 use A, a total of 400 use B, and a total of 450 use C.

Now
People who use only product A =
Total people who use A - ( people who use A & B ) - ( people who use A & C ) - ( people who use A , B & C )
= 400 - 125 - 125 -75
=75

People who use only product B =
Total people who use B - ( people who use A & B ) - ( people who use B & C ) - ( people who use A , B & C )
= 400 - 125 - 100 - 75
= 100

Question is product A or product B or both
So People who use only product A +
People who use only product B +
people who use A & B
75 + 100 +125 = 300

300 is 30% of 1000 people who were asked!

Ans C.

Thanks Suyog for a quick reply! But as u said -

n a marketing survey for products A, B, and C, 1,000 people were asked which of the products, if any, they use.

How r u getting that 1000? To me total no is coming nearly 825 using the formula -
A u B u C = A + B + C - (A n B) - (B n C) - (C n A) - (A n B n C)

camitava wrote:Thanks Suyog for a quick reply! But as u said -

n a marketing survey for products A, B, and C, 1,000 people were asked which of the products, if any, they use.

How r u getting that 1000? To me total no is coming nearly 825 using the formula -
A u B u C = A + B + C - (A n B) - (B n C) - (C n A) - (A n B n C)

I guess the formula should be
A u B u C = A + B + C - (A n B) - (B n C) - (C n A) +(A n B n C)
while deleting [-(A n B) - (B n C) - (C n A)] you have removed the center intersection AnBnc thrice, and this evens out the addition of the center zone in A+B+C, now you need to add the center zone (AnBnC)

Yop, gmatrant! My apology. The formula will be -
A u B u C = A + B + C - (A n B) - (B n C) - (C n A) +(A n B n C)
But still my question remains unanswered. How u r getting that A u B u C = 1000. Pls give me some suggestions.