A mathematics teacher calculated the total marks obtained by 35 students of 8th class . The average marks of the students were 72. But 36 marks for Reena was calculated in place of 86 obtained by her. What was the correct average of all the students? 

In a class of 50 students there are 27 girls. The average weight of these girls is 45 kg and average weight of the full class is 49.6 kgs. What is the average weight of the boys of the class?

The average age of 6 members of a family is 25 years. If the youngest member of the family is 15 years, old then what was the average age (in years) of the family at the time of the birth of the youngest members?

The owner of a bike buys petrol for 3 years continuously at Rs 64, Rs 80 and Rs 320 per litre respectively. If he spends Rs 32,000 every year buying petrol, what is the average price per litre of petrol?

The average of ten numbers is 72. The average of the first four numbers is 69 and that of the next three number is 74. The 8^th number is 6 more than the 9^th number and 12 more than the 10^th number. What is the average of the 8^th and 9^th numbers?

The average weight of three men is increased by 4 kg when one of them, whose weight is 100 kg, is replaced by another man. What is the weight of the new man? 

The average of five numbers is  27.  If one  number is excluded. The average becomes 25. The excluded number is

There are 1600 students in a college, whose average weight is 50 kg. If average weight of boys is 54 kg. and average weight of girls is 38 kg. Then find the number of girls in the school.