What approximate value should come at place of the question mark(?) in the following question?

In solving a problem, one student makes a mistake in the coefficient of the first degree term and obtains – 9 and – 1 for the roots. Another student makes a mistake in the constant term of the equation and obtains 8 and 2 for the roots. The correct equation was 

A number of friends decided to go on picnic and planned to spend Rs. 108 on eatables. Three of them however did not turn up. As a consequence, each one of the remaining had to contribute Rs 3. extra. The number of them who attended the picnic was:

Mr. Girdhar spends 50 % of his monthly income on household items and out of the remaining he spends 50% on transport 25% on entertainment, 10% on sports and remaining amount of Rs.900 is saved. What is Mr.Giridhar's monthly income? 

A shopkeeper has 11 books of same cost price. He sells the first book at certain price, then he sells second book at a price which is ₹ 1 less than the selling price of first book and then he sells third book at a price which is ₹1 less than the selling price of second book. Following this pattern, he sold all 11 books. If he sells sixth book at its cost price. Find the overall percent profit or loss on selling all 11 books. 

The average salary of all the staff in an office of a corporate house is Rs 5,000. The average salary of the officers is Rs 14,000 and that of the rest is Rs 4,000. If the total number of staff is 500, the number of officers is