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Finding the Fourth Proportional to 938.86, 1,407.20 and 390.36

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Solution

The fourth proportional to 938.86, 1,407.20 and 390.36 is: 585.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    938.86 : 1,407.20 = 390.36 : x
  2. Step 2: Convert to fraction form
    938.86/1,407.20 = 390.36/x
  3. Step 3: Cross multiply
    938.86x = 1,407.20 × 390.36
  4. Step 4: Simplify right side
    938.86x = 549,314.59
  5. Step 5: Solve for x
    x = 549,314.59/938.86
  6. Step 6: Final answer
    x = 585.09

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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.