Find the sum of the following to n terms: 7 + 77 + 777 + 7777 + ………

Find the sum of n terms of series whose mth term is 2^m + 2m

If the first term, common ratio and the last term of a G.P. are a, r and l respectively, then the nth term from the end of the G.P. is given by :

1. lr^{n - 1}

2. lr^{1 - n}

3. $\dfrac{l}{r^{1 - n}}$

4. $\dfrac{l}{r^{n + 1}}$

The product of n terms of a G.P. with first term a and common ratio r, when r = 1, is :

1. $\dfrac{a(r^n-1)}{r-1}$

2. na

3. arⁿ

4. aⁿ