NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 5: Arithematic Progressions - Exercise 5.1
Question 15

Question.  15

If the first term of an AP is \(-5\) and the common difference is \(2\), then the sum of the first 6 terms is

(A)

0

(B)

5

(C)

6

(D)

15

Detailed Answer with Explanation:

We are asked to find the sum of the first 6 terms of an Arithmetic Progression (AP).

Step 1: Recall the formula for the sum of the first \(n\) terms of an AP:

\[ S_n = \dfrac{n}{2} \big(2a + (n-1)d \big) \]

where \(a\) = first term, \(d\) = common difference, \(n\) = number of terms.

Step 2: Here, \(a = -5\), \(d = 2\), \(n = 6\).

Step 3: Substitute these values into the formula:

\[ S_6 = \dfrac{6}{2} \big(2(-5) + (6-1)(2) \big) \]

Step 4: Simplify step by step:

\(\dfrac{6}{2} = 3\)

Inside the bracket: \(2(-5) + 5 \cdot 2 = -10 + 10 = 0\)

Step 5: Multiply: \(3 \times 0 = 0\).

Final Answer: The sum of the first 6 terms is 0.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 5: Arithematic Progressions – Exercise 5.1 | Detailed Answers