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Finding the Fourth Proportional to 521.09, 780.82 and 390.88

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Solution

The fourth proportional to 521.09, 780.82 and 390.88 is: 585.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    521.09 : 780.82 = 390.88 : x
  2. Step 2: Convert to fraction form
    521.09/780.82 = 390.88/x
  3. Step 3: Cross multiply
    521.09x = 780.82 × 390.88
  4. Step 4: Simplify right side
    521.09x = 305,206.92
  5. Step 5: Solve for x
    x = 305,206.92/521.09
  6. Step 6: Final answer
    x = 585.71

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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.