In a market research project, 20% opted for Nirma detergent whereas 60% opted for Surf Blue detergent. The remaining individuals were not certain. If the difference between those who opted for Surf Blue and those who were uncertain was 720, how many respondents were covered in the survey ?

A. 1440

B. 1800

C. 3600

D. Data inadequate

Answer: Option B

Solution(By Examveda Team)

Let the total number of respondents be $$x$$
Percentage of uncertain individuals :
= [100 - (20 + 60)]%
= 20%
∴ 60% of $$x$$ - 20% of $$x$$ = 720
⇒ 40% of $$x$$ = 720
⇒ $$\frac{{40x}}{{100}}$$ = 720
⇒ $$x$$ = $$\left( {\frac{{720 \times 100}}{{40}}} \right)$$
⇒ $$x$$ = 1800