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Finding the Fourth Proportional to 685.68, 1,028.60 and 429.20

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Solution

The fourth proportional to 685.68, 1,028.60 and 429.20 is: 643.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.68 : 1,028.60 = 429.20 : x
  2. Step 2: Convert to fraction form
    685.68/1,028.60 = 429.20/x
  3. Step 3: Cross multiply
    685.68x = 1,028.60 × 429.20
  4. Step 4: Simplify right side
    685.68x = 441,475.12
  5. Step 5: Solve for x
    x = 441,475.12/685.68
  6. Step 6: Final answer
    x = 643.85

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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.