Math Problem Statement

Find the sum of the first 10 terms of the sequence where the first term is 2 and each subsequent term is obtained by adding the previous term to 3."

Solution

To find the sum of the first 10 terms of the sequence where the first term a1=2a_1 = 2 and each subsequent term increases by d=3d = 3, we use the formula for the sum of an arithmetic sequence:

Sn=n2(a1+an)S_n = \frac{n}{2} \cdot (a_1 + a_n)

Step 1: Calculate the 10th term (a10a_{10})

The formula for the nn-th term of an arithmetic sequence is:

an=a1+(n1)da_n = a_1 + (n-1)d

Substitute a1=2a_1 = 2, d=3d = 3, and n=10n = 10:

a10=2+(101)3=2+27=29a_{10} = 2 + (10-1) \cdot 3 = 2 + 27 = 29

Step 2: Calculate the sum of the first 10 terms (S10S_{10})

Substitute n=10n = 10, a1=2a_1 = 2, and a10=29a_{10} = 29 into the sum formula:

S10=102(2+29)=531=155S_{10} = \frac{10}{2} \cdot (2 + 29) = 5 \cdot 31 = 155

Final Answer:

The sum of the first 10 terms is:

155\boxed{155}

Would you like further explanation or related examples? Here are five related questions for practice:

  1. Find the sum of the first 20 terms of the same sequence.
  2. What is the sum of the first 10 terms of the sequence if the common difference is 5 instead of 3?
  3. Derive the general formula for the sum of the first nn terms of this sequence.
  4. Calculate the 15th term of this sequence.
  5. What is the difference between the sum of the first 10 terms and the first 5 terms?

Tip: Always double-check arithmetic sequences by writing out the first few terms to ensure the common

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Summation

Formulas

Sum of an arithmetic sequence: S_n = (n / 2) * (a_1 + a_n)
n-th term of an arithmetic sequence: a_n = a_1 + (n-1)d

Theorems

Properties of Arithmetic Sequences

Suitable Grade Level

Grades 6-8