Mark the correct alternative in the following:

The first and last term of an A.P. are a and l respectively. If S is the sum of all terms of the A.P. and the common difference is given by , then k =

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In n arithmetic means are inserted between 1 and 31 such that the ratio of the first mean and nth mean is 3 : 29, then the value of n is

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Let denote the sum of n terms of an A.P. whose first term is a. If the common difference d is given by , then k =

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If the sum of first n even natural numbers is equal to k times the sum of first n odd natural numbers, then k =

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If the first, second and last term of an A.P. are a, b and 2a respectively, then its sum is