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Finding the Fourth Proportional to 715.69, 987.64 and 420.90

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Solution

The fourth proportional to 715.69, 987.64 and 420.90 is: 580.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.69 : 987.64 = 420.90 : x
  2. Step 2: Convert to fraction form
    715.69/987.64 = 420.90/x
  3. Step 3: Cross multiply
    715.69x = 987.64 × 420.90
  4. Step 4: Simplify right side
    715.69x = 415,697.68
  5. Step 5: Solve for x
    x = 415,697.68/715.69
  6. Step 6: Final answer
    x = 580.83

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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.