A train covers a certain distance. Had it moved 4 kmh"1 faster, it would have taken 1.5 hrs less. If it had moved 6 kmh'1 slower, it would have taken 3 hrs more. What is the distance the train covers ?
A contractor decided to build a bridge in 35 days. He employed 60 men in the beginning and 40 more after 17 days and completed the work on time. If he had not employed the additional men, how many days behind schedule would it have been finished ?
The average age of all the students of a class is 15 years. The average age of the boys of the class is 17 years and that of the girls is 12 years. If the number of girls in the class is 3 6 then what is the number of boys in the class ?