Step-2

Title: Consecutive terms of A.P

Grade: 9-a Lesson: S4-L5

Explanation: Hello Students, time to practice and review the steps for the problem.

Lesson Steps

Step Type Explanation Answer

1

Problem

How many terms of the A.P. 20,16,12,… be taken so that their sum is zero?

2

Step

The first term

\$ a = 20 \$

3

Formula:

Common difference

\$ d = a_2 - a_1 = 16 - 20 = -4\$

4

Formula:

The \$n^(th)\$ term sum is given by

\$ S_n = n/2(2a + (n-1)d)\$

5

Hint

Substitute the values

\$ 0 = n/2(2(20) + (n-1)-4) \$

6

Step

After simplification

\$0 = n/2(40 - 4n + 4 ) \$

7

Step

After simplification

\$ 0 = n/2(44 - 4n)\$

8

Step

After simplification

\$ 0 = 44 - 4n\$

9

Step

After simplification

\$ 4n = 44\$

10

Step

After simplification

\$ n = \cancel44^11/\cancel4^1 \$

11

Step

After cancellation

\$ n = 11\$

12

Answer

A

Tutor: Questions

Seq Type Question Audio

1

Problem

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2

Clue

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3

Hint

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4

Step

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5

Step

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