Math Problem Statement

Consider a finite arithmetic sequence of positive integers. Among its terms are the numbers 28, 52 and 82. The sum of all terms in the sequence is 1769. Find the smallest and largest terms in the sequence.

Solution

We are given an arithmetic sequence of positive integers that contains the numbers 28, 52, and 82 as terms. The sum of all terms in the sequence is 1769. We need to find the smallest and largest terms in the sequence.

Step 1: General form of an arithmetic sequence

The general form of an arithmetic sequence is:

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

where:

  • ana_n is the nn-th term,
  • a1a_1 is the first term,
  • dd is the common difference.

Step 2: Equation setup using known terms

Let’s assume the position of 28, 52, and 82 in the sequence are aia_i, aja_j, and aka_k respectively. Therefore:

ai=a1+(i1)d=28a_i = a_1 + (i-1) d = 28 aj=a1+(j1)d=52a_j = a_1 + (j-1) d = 52 ak=a1+(k1)d=82a_k = a_1 + (k-1) d = 82

From these, we can subtract the equations to find dd.

Subtract the first equation from the second:

(a1+(j1)d)(a1+(i1)d)=5228(a_1 + (j-1) d) - (a_1 + (i-1) d) = 52 - 28 (ji)d=24sod=24ji(j-i)d = 24 \quad \text{so} \quad d = \frac{24}{j-i}

Subtract the second equation from the third:

(a1+(k1)d)(a1+(j1)d)=8252(a_1 + (k-1) d) - (a_1 + (j-1) d) = 82 - 52 (kj)d=30sod=30kj(k-j) d = 30 \quad \text{so} \quad d = \frac{30}{k-j}

Now we have two equations for dd:

  1. d=24jid = \frac{24}{j-i}
  2. d=30kjd = \frac{30}{k-j}

Step 3: Solving for positions

Let’s try to find the smallest integer values for jij - i and kjk - j that make the common difference dd consistent in both equations.

Assume ji=2j - i = 2. Then:

d=242=12d = \frac{24}{2} = 12

Substitute d=12d = 12 into the second equation:

30=(kj)12kj=3012=2.530 = (k-j) \cdot 12 \quad \Rightarrow \quad k - j = \frac{30}{12} = 2.5

Since kjk - j must be an integer, this assumption leads to a contradiction. Therefore, try different values for jij - i.

Continue with

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Algebra

Formulas

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

Theorems

Arithmetic Progression

Suitable Grade Level

Grades 9-12