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Finding the Fourth Proportional to 661.72, 991.90 and 386.98

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Solution

The fourth proportional to 661.72, 991.90 and 386.98 is: 580.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.72 : 991.90 = 386.98 : x
  2. Step 2: Convert to fraction form
    661.72/991.90 = 386.98/x
  3. Step 3: Cross multiply
    661.72x = 991.90 × 386.98
  4. Step 4: Simplify right side
    661.72x = 383,845.46
  5. Step 5: Solve for x
    x = 383,845.46/661.72
  6. Step 6: Final answer
    x = 580.07

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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.