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Finding the Fourth Proportional to 1,128.48, 1,691.28 and 938.40

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Solution

The fourth proportional to 1,128.48, 1,691.28 and 938.40 is: 1,406.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,128.48 : 1,691.28 = 938.40 : x
  2. Step 2: Convert to fraction form
    1,128.48/1,691.28 = 938.40/x
  3. Step 3: Cross multiply
    1,128.48x = 1,691.28 × 938.40
  4. Step 4: Simplify right side
    1,128.48x = 1,587,097.15
  5. Step 5: Solve for x
    x = 1,587,097.15/1,128.48
  6. Step 6: Final answer
    x = 1,406.40

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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.