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Finding the Fourth Proportional to 661.78, 991.50 and 387.64

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Solution

The fourth proportional to 661.78, 991.50 and 387.64 is: 580.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.78 : 991.50 = 387.64 : x
  2. Step 2: Convert to fraction form
    661.78/991.50 = 387.64/x
  3. Step 3: Cross multiply
    661.78x = 991.50 × 387.64
  4. Step 4: Simplify right side
    661.78x = 384,345.06
  5. Step 5: Solve for x
    x = 384,345.06/661.78
  6. Step 6: Final answer
    x = 580.77

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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.