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 of a collection of 20 measurements was calculated to be 56 cm . But later it was found that a mistake had occurred in one of the measurements which was recorded as 64 cm, but should have been 61 cm. The correct average must be: 

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

The present age of a father is 3 years more than three times the age of his son. Three years hence, father's age will be 10 years more than twice the age of the son. The father's age is: 

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 weight of 8 people is increased by 2 kg when a new person comes in place of the person who weighs 50 kg. What is the weight of the newcomer?

The average weight of A, B, and C is 52 kg. If the average weight of B and C is 44 kg and that of C and A is 46 kg, then what will be the weight of C?

The average of four consecutive odd numbers is 36. What is the smallest of these numbers?