On a particular day of a trade fair, 35000 visitors had visited the fair. The amount collected at the entrance counter was Rs. 9,50,000. The entrance fee was at the rate of Rs. 40 for an adult and Rs.20 for a child. If 10% of the visitors had used free passes, the number of children who visited the fair is
Number of visitors who paid for the ticket = $$\frac{90}{100}\times35000=31500$$
Let number of children be $$x$$ and number of adults = $$(31500-x)$$
According to ques,
=> $$40(31500-x)+20x=9,50,000$$
=> $$12,60,000-20x=9,50,000$$
=> $$20x=3,10,000$$
=> $$x=\frac{310000}{20}=15,500$$
=> Ans - (B)