Arithmetic Sequence: Is 29 the nth Term When a₁=1.5 and d=3?

Arithmetic Sequences with Non-Integer Solutions

Given a series whose first element is 1.5.

Each element of the series is greater by 3 of its predecessor.

Is the number 29 an element in the series?

If so, please indicate your place in the series.

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Is the number 29 in the sequence?
00:06 Let's use the sequence formula
00:18 Let's substitute appropriate values according to the given data and solve
00:30 If the value of N is a positive whole number, then the number is a term in the sequence
00:43 Let's properly open the parentheses and multiply by each factor
00:57 We want to isolate N
01:24 The value of N is a decimal number, therefore it's not a term in the sequence
01:28 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given a series whose first element is 1.5.

Each element of the series is greater by 3 of its predecessor.

Is the number 29 an element in the series?

If so, please indicate your place in the series.

2

Step-by-step solution

To determine whether the number 29 is an element of the series, we start by recognizing that the problem involves an arithmetic sequence. In such a sequence, each term is generated by adding a constant difference to the previous term. Here, the first term a1 a_1 is 1.5 1.5 , and the common difference d d is 3 3 .

The formula for the nth term of an arithmetic sequence is given by:

an=a1+(n1)d a_n = a_1 + (n-1) \cdot d

We need to check if 29 is one of the terms of this series, so we set an=29 a_n = 29 and solve for n n :

29=1.5+(n1)3 29 = 1.5 + (n-1) \cdot 3

Subtract 1.5 from both sides:

291.5=(n1)3 29 - 1.5 = (n-1) \cdot 3

27.5=(n1)3 27.5 = (n-1) \cdot 3

Divide both sides by 3 to solve for n1 n - 1 :

n1=27.53 n-1 = \frac{27.5}{3}

n1=9.1666 n-1 = 9.1666\ldots

Add 1 to find n n :

n=10.1666 n = 10.1666\ldots

Since n n is not an integer, the number 29 does not appear as an element in this sequence. Arithmetic sequences only have integer positions for their terms, so n n must be a whole number for 29 to be a term. As a result, the correct answer is:

No

3

Final Answer

No

Key Points to Remember

Essential concepts to master this topic
  • Formula: Use a_n = a₁ + (n-1)d to find any term
  • Technique: Set 29 = 1.5 + (n-1)×3 and solve for n
  • Check: If n is not a whole number, the value is not in the sequence ✓

Common Mistakes

Avoid these frequent errors
  • Accepting decimal position numbers as valid
    Don't think n = 10.167 means 29 is between the 10th and 11th terms = wrong conclusion! Position numbers in sequences must be positive integers only. Always verify that your calculated n value is a whole number.

Practice Quiz

Test your knowledge with interactive questions

Is there a term-to-term rule for the sequence below?

18 , 22 , 26 , 30

FAQ

Everything you need to know about this question

What does it mean when I get a decimal for n?

+

When you solve for n and get a decimal like 10.167, it means the target number falls between two consecutive terms in the sequence. Since sequence positions must be whole numbers, the target is not in the sequence.

How can I find what terms are closest to 29?

+

Calculate the 10th and 11th terms! The 10th term: a10=1.5+9×3=28.5 a_{10} = 1.5 + 9×3 = 28.5 and 11th term: a11=1.5+10×3=31.5 a_{11} = 1.5 + 10×3 = 31.5 . So 29 falls between these values.

Why can't position numbers be decimals?

+

Think about it logically: you can have the 1st term, 2nd term, 3rd term, etc. But what would the 2.5th term mean? Sequence positions represent counting numbers, which are always whole numbers.

What if the first term or common difference were different?

+

The same process applies! Always substitute into an=a1+(n1)d a_n = a_1 + (n-1)d and solve for n. If n is a positive integer, the number is in the sequence. If not, it isn't!

Can I use this method for any arithmetic sequence?

+

Absolutely! This algebraic approach works for any arithmetic sequence. Just identify a1 a_1 (first term) and d d (common difference), then solve an=a1+(n1)d a_n = a_1 + (n-1)d for your target value.

🌟 Unlock Your Math Potential

Get unlimited access to all 18 Series questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations