Math Problem Statement

در بین اعداد -5 و 35/4، تعداد 4 واسطه حسابی درج کرده‌ایم. بزرگ‌ترین عدد در بین این 4 واسطه حسابی، کدام است؟

Solution

The question appears to be in Persian, and it translates to:

"Among the numbers -5 and 354\frac{35}{4}, we've inserted 4 arithmetic means. Which of these is the largest number among these 4 arithmetic means?"

The answer choices provided are:

  1. 294\frac{29}{4}
  2. 5-5
  3. 234\frac{23}{4}
  4. 132\frac{13}{2}

To solve this:

  1. Identify the Terms in the Sequence: We have the first term a=5a = -5 and the last term l=354l = \frac{35}{4}, with 4 arithmetic means in between. Therefore, there are 6 terms in total, so this is an arithmetic sequence with 6 terms.

  2. Determine the Common Difference: For an arithmetic sequence, the common difference dd can be found by the formula: d=lan1d = \frac{l - a}{n - 1} where nn is the total number of terms. Here, n=6n = 6, so: d=354(5)61=354+55d = \frac{\frac{35}{4} - (-5)}{6 - 1} = \frac{\frac{35}{4} + 5}{5} Converting 5-5 to quarters: d=354+2045=5545=5520=114d = \frac{\frac{35}{4} + \frac{20}{4}}{5} = \frac{\frac{55}{4}}{5} = \frac{55}{20} = \frac{11}{4}

  3. Calculate the Sequence Terms: The terms of the sequence are:

    • First term: a=5a = -5
    • Second term: a+d=5+114=204+114=94a + d = -5 + \frac{11}{4} = -\frac{20}{4} + \frac{11}{4} = -\frac{9}{4}
    • Third term: a+2d=5+2×114=5+224=204+224=24=12a + 2d = -5 + 2 \times \frac{11}{4} = -5 + \frac{22}{4} = -\frac{20}{4} + \frac{22}{4} = \frac{2}{4} = \frac{1}{2}
    • Fourth term: a+3d=5+3×114=5+334=204+334=134a + 3d = -5 + 3 \times \frac{11}{4} = -5 + \frac{33}{4} = -\frac{20}{4} + \frac{33}{4} = \frac{13}{4}
    • Fifth term: a+4d=5+4×114=5+444=204+444=244=6a + 4d = -5 + 4 \times \frac{11}{4} = -5 + \frac{44}{4} = -\frac{20}{4} + \frac{44}{4} = \frac{24}{4} = 6
    • Sixth term (last term): l=354l = \frac{35}{4}
  4. Identify the Largest Term Among the Means: Among the 4 arithmetic means, the largest value is the fifth term: 134=6\frac{13}{4} = 6

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequence
Arithmetic Mean

Formulas

d = (l - a) / (n - 1)
nth term formula: a + (n-1)d

Theorems

Arithmetic Sequence Formula

Suitable Grade Level

Grades 9-11