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? 

A car travel to a place 150 km away at an average speed of 50 km/hr and returns it 30 km/hr. What is the average speed of the whole journey?

A batsman makes a score of 87 runs in the 17^th match and thus  increases his average by 3. Find his average after 17^th match.

In an examination, 40% of the candidates write their answers in Urdu and the rest in Marathi. The average marks of the candidates writing in Urdu is 74 and the average marks of the candidates writing in Marathi is 77. What are the average marks of all the candidates? 

Three science classes A, B and C take a Science test. The average score of class A is 83. The average score of class B is 76. The average score of class C is 85. The average score of class A and B is 79 and average score of class B and C is 81. Then the average score of classes A, B and C is

The average age of 30 students of a class is 15 years. A 20-year-old student left the class and replaced by two new students, whose age difference is 5 years. If the average age of all students is 15 years, then what will be ratio of young student to elder students. 

What decimal of a week is an hour? 

Average age of 6 boys is 14 years. Average age of 11 girls is 12 years. What is the average age (in years) of all boys and girls?