The product of two consecutive odd numbers is 399. Find the lower of them.

The average of some natural numbers is 15. If 30 is added to first number and 5 is subtracted from the last number, the average become 17.5. then the numbers of natural numbers is :

The average of five natural numbers is p. If the next three numbers are included then how much the average of these 8 numbers exceeds than the average p?

The arithmetic mean of the following data is .

23, 17,20,19,21

Direction : What value should come in the place of question mark (?) in the following questions?

11283 + 25 % of ? + 727 = 13280 

Select the number triad that is analogous to the given triads.
 (64, 8, 65), (125, 27, 89)

The least number, which must be added to 6709 to make it exactly divisible by 9, is 

Three numbers are such that if the average of any two of them is added to the third number, the sums obtained are 168, 174 and 180 respectively. What is the average of the original three numbers?