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Finding the Fourth Proportional to 480.78, 721.20 and 138.78

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Solution

The fourth proportional to 480.78, 721.20 and 138.78 is: 208.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    480.78 : 721.20 = 138.78 : x
  2. Step 2: Convert to fraction form
    480.78/721.20 = 138.78/x
  3. Step 3: Cross multiply
    480.78x = 721.20 × 138.78
  4. Step 4: Simplify right side
    480.78x = 100,088.14
  5. Step 5: Solve for x
    x = 100,088.14/480.78
  6. Step 6: Final answer
    x = 208.18

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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.