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Finding the Fourth Proportional to 312.40, 431.40 and 209.20

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Solution

The fourth proportional to 312.40, 431.40 and 209.20 is: 288.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    312.40 : 431.40 = 209.20 : x
  2. Step 2: Convert to fraction form
    312.40/431.40 = 209.20/x
  3. Step 3: Cross multiply
    312.40x = 431.40 × 209.20
  4. Step 4: Simplify right side
    312.40x = 90,248.88
  5. Step 5: Solve for x
    x = 90,248.88/312.40
  6. Step 6: Final answer
    x = 288.89

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.