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Finding the Fourth Proportional to 815.20, 1,123.68 and 640.32

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Solution

The fourth proportional to 815.20, 1,123.68 and 640.32 is: 882.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.20 : 1,123.68 = 640.32 : x
  2. Step 2: Convert to fraction form
    815.20/1,123.68 = 640.32/x
  3. Step 3: Cross multiply
    815.20x = 1,123.68 × 640.32
  4. Step 4: Simplify right side
    815.20x = 719,514.78
  5. Step 5: Solve for x
    x = 719,514.78/815.20
  6. Step 6: Final answer
    x = 882.62

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.