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Finding the Fourth Proportional to 1,405.20, 1,939.08 and 815.76

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Solution

The fourth proportional to 1,405.20, 1,939.08 and 815.76 is: 1,125.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,405.20 : 1,939.08 = 815.76 : x
  2. Step 2: Convert to fraction form
    1,405.20/1,939.08 = 815.76/x
  3. Step 3: Cross multiply
    1,405.20x = 1,939.08 × 815.76
  4. Step 4: Simplify right side
    1,405.20x = 1,581,823.90
  5. Step 5: Solve for x
    x = 1,581,823.90/1,405.20
  6. Step 6: Final answer
    x = 1,125.69

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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.