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Finding the Fourth Proportional to 715.28, 987 and 420.64

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Solution

The fourth proportional to 715.28, 987 and 420.64 is: 580.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.28 : 987 = 420.64 : x
  2. Step 2: Convert to fraction form
    715.28/987 = 420.64/x
  3. Step 3: Cross multiply
    715.28x = 987 × 420.64
  4. Step 4: Simplify right side
    715.28x = 415,171.68
  5. Step 5: Solve for x
    x = 415,171.68/715.28
  6. Step 6: Final answer
    x = 580.43

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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.