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Finding the Fourth Proportional to 715.67, 987.64 and 420.87

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Solution

The fourth proportional to 715.67, 987.64 and 420.87 is: 580.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.67 : 987.64 = 420.87 : x
  2. Step 2: Convert to fraction form
    715.67/987.64 = 420.87/x
  3. Step 3: Cross multiply
    715.67x = 987.64 × 420.87
  4. Step 4: Simplify right side
    715.67x = 415,668.05
  5. Step 5: Solve for x
    x = 415,668.05/715.67
  6. Step 6: Final answer
    x = 580.81

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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.