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Finding the Fourth Proportional to 687.90, 1,031.96 and 380.05

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Solution

The fourth proportional to 687.90, 1,031.96 and 380.05 is: 570.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.90 : 1,031.96 = 380.05 : x
  2. Step 2: Convert to fraction form
    687.90/1,031.96 = 380.05/x
  3. Step 3: Cross multiply
    687.90x = 1,031.96 × 380.05
  4. Step 4: Simplify right side
    687.90x = 392,198.64
  5. Step 5: Solve for x
    x = 392,198.64/687.90
  6. Step 6: Final answer
    x = 570.14

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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.