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?

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? 

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

A certain sum is deposited for 4 years at a rate of 10% per annum on compound interest compounded annually. The difference between ihe interest at the end of 2 years and that at the end of 4 years is ₹5,082. Find the sum (in ₹).

What is the average of all odd natural numbers less than 100?

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 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 6 numbers is 20. If a number is removed then average becomes 15. In place of removed number by adding a number 39 the average of new 6 number will be__