Some students (only boys and girls) from different schools1 appeared for an Olympiad exam. 20% of the boys and 15% of the girls failed the exam. The number of boys who passed the exam was 70 more than that of the girls who passed the exam'. A total of 90 students failed. Find the number of students that appeared for the exam.

A Navy captain going away from a lighthouse at the speed of 4[(73) -1] m/s. He observes that it takes him 1 minute to change the angle of elevation of the top of the lighthouse from 60 ° to 45 °. What is the height (in meters) of the lighthouse? 

A sum of money placed at compound interest triples itself in 9 year. In how many years will if amount to 243 times itself?

The number, whose square is equal to the difference between the squares of 975 and 585, is: 

Find the value of given expression.

3 – (– 6) {– 2 – 9 – 3} ÷ 7{1 + (– 2) (– 1)}

The average weight of 15 oarsmen in a boat is increased by 1.6 kg when one of the crews, whose weighs 42 kg is replaced by a new man. Find the weight of the new man (in kg). 

A person bought pens at 25 for a rupee and sold at 15 for a rupee. What is his profit percentage?