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Finding the Fourth Proportional to 687.20, 1,030.20 and 378.68

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Solution

The fourth proportional to 687.20, 1,030.20 and 378.68 is: 567.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.20 : 1,030.20 = 378.68 : x
  2. Step 2: Convert to fraction form
    687.20/1,030.20 = 378.68/x
  3. Step 3: Cross multiply
    687.20x = 1,030.20 × 378.68
  4. Step 4: Simplify right side
    687.20x = 390,116.14
  5. Step 5: Solve for x
    x = 390,116.14/687.20
  6. Step 6: Final answer
    x = 567.69

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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.