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Finding the Fourth Proportional to 390.40, 538.64 and 280.16

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Solution

The fourth proportional to 390.40, 538.64 and 280.16 is: 386.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.40 : 538.64 = 280.16 : x
  2. Step 2: Convert to fraction form
    390.40/538.64 = 280.16/x
  3. Step 3: Cross multiply
    390.40x = 538.64 × 280.16
  4. Step 4: Simplify right side
    390.40x = 150,905.38
  5. Step 5: Solve for x
    x = 150,905.38/390.40
  6. Step 6: Final answer
    x = 386.54

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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.