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Finding the Fourth Proportional to 390.40, 538.80 and 383.20

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Solution

The fourth proportional to 390.40, 538.80 and 383.20 is: 528.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.40 : 538.80 = 383.20 : x
  2. Step 2: Convert to fraction form
    390.40/538.80 = 383.20/x
  3. Step 3: Cross multiply
    390.40x = 538.80 × 383.20
  4. Step 4: Simplify right side
    390.40x = 206,468.16
  5. Step 5: Solve for x
    x = 206,468.16/390.40
  6. Step 6: Final answer
    x = 528.86

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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.