Sequences and S...

The number of terms of the A.P. 3,7,11,15.... to be taken so that the sum is 406 is

There are 15 terms in an arithmetic progression. Its first term is 5 and their sum is 390. The middle term is

If the sum of the 10 terms of an A.P. is 4 times to the sum of its 5 terms, then the ratio of first term and common difference is

Three number are in A.P such that their sum is 18 and sum of their squares is 158. The greatest number among them is

If A be an arithmetic mean between two numbers and S be the sum of n arithmetic means between the same numbers, then

The mean of the series a,a + nd, a + 2nd is

If f (x + y, x - y) = xy then the arithmetic mean of f (x,y) and f (y,x) is

If log 2, log(2ⁿ – 1) and log(2ⁿ + 3) are in A.P. then n =

If the sides of a right angled triangle are in A.P then the sides are proportional to

Three numbers are in A.P. whose sum is 33 and product is 792, then the smallest number from these numbers is