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Finding the Fourth Proportional to 209.65, 314.48 and 86.31

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Solution

The fourth proportional to 209.65, 314.48 and 86.31 is: 129.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.65 : 314.48 = 86.31 : x
  2. Step 2: Convert to fraction form
    209.65/314.48 = 86.31/x
  3. Step 3: Cross multiply
    209.65x = 314.48 × 86.31
  4. Step 4: Simplify right side
    209.65x = 27,142.77
  5. Step 5: Solve for x
    x = 27,142.77/209.65
  6. Step 6: Final answer
    x = 129.47

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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.