Math Problem Statement

Find the number of terms in an arithmetic sequence where the sum of all terms is given, with the first term being 124, the last term being 111, and the sum of all terms being 4700.

Solution

This problem asks us to find the number of terms in an arithmetic sequence where the sum of all terms is given. Let's solve it step by step.

Given:

  • First term (aa) = 124
  • Last term (ll) = 111
  • Sum of all terms (SnS_n) = 4700
  • Formula for the sum of an arithmetic sequence:
    Sn=n2(a+l)S_n = \frac{n}{2} \cdot (a + l)

Step 1: Substitute known values into the formula:

4700=n2(124+111)4700 = \frac{n}{2} \cdot (124 + 111)

Step 2: Simplify the equation:

4700=n22354700 = \frac{n}{2} \cdot 235

Multiply both sides by 2: 9400=n2359400 = n \cdot 235

Step 3: Solve for nn:

n=9400235=40n = \frac{9400}{235} = 40

Final Answer:

The number of terms in the sequence is 40.


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Related Questions:

  1. What is the common difference of the sequence?
  2. How do you find the nn-th term of an arithmetic sequence?
  3. What happens if the sum is a different value, e.g., 50005000?
  4. How can you verify the number of terms once calculated?
  5. How would the solution change if only the sum and first term were given?

Tip:

In arithmetic sequences, double-check calculations involving the sum formula by ensuring all terms align with the given series endpoints.

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Sum of an Arithmetic Sequence

Formulas

S_n = n/2 * (a + l)

Theorems

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Suitable Grade Level

Grades 7-9