Sum of n terms of an A.P. whose first term and last term are a and l respectively is given by:

1. S_n = $\dfrac{n}{2}(a + l)$

2. S_n = $\dfrac{n}{2}(a − l)$

3. S_n = $\dfrac{n}{2}(2a + l)$

4. S_n = $\dfrac{n}{2}[a + (n − 1)l]$

The sum of first n natural numbers is:

1. $\dfrac{n(n − 1)}{2}$

2. $\dfrac{n(n + 1)}{2}$

3. $\dfrac{n(n + 2)}{2}$

4. $\dfrac{n(n − 2)}{2}$

The nth term of an Arithmetic Progression (A.P.) is 2n + 5. The 10th term is :

1. 7

2. 15

3. 25

4. 45

The first term of an A.P. is 7 and the common difference is 3. The general term of the A.P. is:

1. T_n = 3n − 4

2. T_n = 2n + 5

3. T_n = 3n + 4

4. None of these