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Finding the Fourth Proportional to 431.78, 647.47 and 139.19

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Solution

The fourth proportional to 431.78, 647.47 and 139.19 is: 208.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.78 : 647.47 = 139.19 : x
  2. Step 2: Convert to fraction form
    431.78/647.47 = 139.19/x
  3. Step 3: Cross multiply
    431.78x = 647.47 × 139.19
  4. Step 4: Simplify right side
    431.78x = 90,117.42
  5. Step 5: Solve for x
    x = 90,117.42/431.78
  6. Step 6: Final answer
    x = 208.71

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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.