The ratio of the speeds of the two airplanes is 7:15. If the first airplane covers a distance of 1050 km in 3 hours, what is the speed of the second airplane?

The product of the LCM and HCF of two numbers is 24. The difference of the two numbers is 2. Find the numbers? 

A man rides his vehicle at the rate of 36 km/hr but stops for 12 minutes, to change parts at the end of every 14^th  km,what will be the timed taken to cover a distance of 90 km?

B got 20% marks less than A. What per cent marks did A got more than B? 

Arun purchased 30 kg. of rice at the rate of Rs. 17.50 per kg. and another Rs. 30 kg. at a certain rate. He mixed the two and sold the entire quantity at the rate Rs. 18.60 per kg. and made 20% overall profit. At what price per kg. did he pruchase the lot of another 30 kg. rice?

A shopkeeper sold an item at a 10% loss after giving a discount equal to half the marked price. Then the cost price is 

The population of a city is 48,600. If there is a 25% increase in the first year and a reduction of 8% in the second year, then what will be the population of this city at the end of 2 years?

The average of marks scored by the students of a class is 68. The average of marks of the girls in the class is 80 and that of the boys is 60. What is the percentage of boys in the class?