Chapter 11: Q39. (page 581)

Find the indicated term of each arithmetic sequence.
$a_{21}$ for 121, 118, 115, …

Short Answer

Expert verified

The indicated term of the arithmetic sequence is61.

Step by step solution

Step 1. Given Information.

Given arithmetic sequence is 121, 118, 115, …

Step 2. Calculation.

The n^th term of an arithmetic sequence is given by $a_{n} = a_{1} + (n - 1) d$ .

Here the first term is $a_{1} = 121$

The difference between the first two terms is $118 - 121 = - 3$

The difference between the next two terms is $115 - 118 = - 3$

The common difference is $d = - 3$

And the required term is $n = 21$

Plugging the values in the formula:

$\begin{array}{l} a_{n} = a_{1} + (n - 1) d \\ a_{21} = 121 + (21 - 1) (- 3) \\ a_{21} = 121 + (20) (- 3) \\ a_{21} = 121 - 60 \\ a_{21} = 61 \end{array}$

Step 3. Conclusion.

Hence, the indicated term of the arithmetic sequence is 61.

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Find the indicated term of each arithmetic sequence.
$a_{21}$ for 121, 118, 115, …

Short Answer

Step by step solution

Step 1. Given Information.

Step 2. Calculation.

Step 3. Conclusion.

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Find the indicated term of each arithmetic sequence.a21for 121, 118, 115, …

Short Answer

Step by step solution

Step 1. Given Information.

Step 2. Calculation.

Step 3. Conclusion.

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Math Textbooks

Probability and Statistics

Decision Maths

Geometry

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Theoretical and Mathematical Physics

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Study anywhere. Anytime. Across all devices.

Find the indicated term of each arithmetic sequence.
$a_{21}$ for 121, 118, 115, …