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Finding the Fourth Proportional to 1,405.71, 1,939.57 and 815.90

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Solution

The fourth proportional to 1,405.71, 1,939.57 and 815.90 is: 1,125.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,405.71 : 1,939.57 = 815.90 : x
  2. Step 2: Convert to fraction form
    1,405.71/1,939.57 = 815.90/x
  3. Step 3: Cross multiply
    1,405.71x = 1,939.57 × 815.90
  4. Step 4: Simplify right side
    1,405.71x = 1,582,495.16
  5. Step 5: Solve for x
    x = 1,582,495.16/1,405.71
  6. Step 6: Final answer
    x = 1,125.76

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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.