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Finding the Fourth Proportional to 715.65, 987.66 and 420.86

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Solution

The fourth proportional to 715.65, 987.66 and 420.86 is: 580.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.65 : 987.66 = 420.86 : x
  2. Step 2: Convert to fraction form
    715.65/987.66 = 420.86/x
  3. Step 3: Cross multiply
    715.65x = 987.66 × 420.86
  4. Step 4: Simplify right side
    715.65x = 415,666.59
  5. Step 5: Solve for x
    x = 415,666.59/715.65
  6. Step 6: Final answer
    x = 580.82

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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.