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Finding the Fourth Proportional to 209.91, 314.85 and 86.51

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Solution

The fourth proportional to 209.91, 314.85 and 86.51 is: 129.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.91 : 314.85 = 86.51 : x
  2. Step 2: Convert to fraction form
    209.91/314.85 = 86.51/x
  3. Step 3: Cross multiply
    209.91x = 314.85 × 86.51
  4. Step 4: Simplify right side
    209.91x = 27,238.79
  5. Step 5: Solve for x
    x = 27,238.79/209.91
  6. Step 6: Final answer
    x = 129.76

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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.