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Finding the Fourth Proportional to 390.80, 580.78 and 390.80

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Solution

The fourth proportional to 390.80, 580.78 and 390.80 is: 580.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.80 : 580.78 = 390.80 : x
  2. Step 2: Convert to fraction form
    390.80/580.78 = 390.80/x
  3. Step 3: Cross multiply
    390.80x = 580.78 × 390.80
  4. Step 4: Simplify right side
    390.80x = 226,968.82
  5. Step 5: Solve for x
    x = 226,968.82/390.80
  6. Step 6: Final answer
    x = 580.78

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.