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Finding the Fourth Proportional to 209.56, 314.40 and 81.28

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Solution

The fourth proportional to 209.56, 314.40 and 81.28 is: 121.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.56 : 314.40 = 81.28 : x
  2. Step 2: Convert to fraction form
    209.56/314.40 = 81.28/x
  3. Step 3: Cross multiply
    209.56x = 314.40 × 81.28
  4. Step 4: Simplify right side
    209.56x = 25,554.43
  5. Step 5: Solve for x
    x = 25,554.43/209.56
  6. Step 6: Final answer
    x = 121.94

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.