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Finding the Fourth Proportional to 938.20, 1,405.68 and 815.68

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Solution

The fourth proportional to 938.20, 1,405.68 and 815.68 is: 1,222.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    938.20 : 1,405.68 = 815.68 : x
  2. Step 2: Convert to fraction form
    938.20/1,405.68 = 815.68/x
  3. Step 3: Cross multiply
    938.20x = 1,405.68 × 815.68
  4. Step 4: Simplify right side
    938.20x = 1,146,585.06
  5. Step 5: Solve for x
    x = 1,146,585.06/938.20
  6. Step 6: Final answer
    x = 1,222.11

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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.