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Finding the Fourth Proportional to 390.72, 581.16 and 389.40

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Solution

The fourth proportional to 390.72, 581.16 and 389.40 is: 579.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.72 : 581.16 = 389.40 : x
  2. Step 2: Convert to fraction form
    390.72/581.16 = 389.40/x
  3. Step 3: Cross multiply
    390.72x = 581.16 × 389.40
  4. Step 4: Simplify right side
    390.72x = 226,303.70
  5. Step 5: Solve for x
    x = 226,303.70/390.72
  6. Step 6: Final answer
    x = 579.20

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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.