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Finding the Fourth Proportional to 485.39, 728.21 and 138.74

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Solution

The fourth proportional to 485.39, 728.21 and 138.74 is: 208.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    485.39 : 728.21 = 138.74 : x
  2. Step 2: Convert to fraction form
    485.39/728.21 = 138.74/x
  3. Step 3: Cross multiply
    485.39x = 728.21 × 138.74
  4. Step 4: Simplify right side
    485.39x = 101,027.78
  5. Step 5: Solve for x
    x = 101,027.78/485.39
  6. Step 6: Final answer
    x = 208.14

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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.