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Finding the Fourth Proportional to 661.78, 991.05 and 430.84

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Solution

The fourth proportional to 661.78, 991.05 and 430.84 is: 645.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.78 : 991.05 = 430.84 : x
  2. Step 2: Convert to fraction form
    661.78/991.05 = 430.84/x
  3. Step 3: Cross multiply
    661.78x = 991.05 × 430.84
  4. Step 4: Simplify right side
    661.78x = 426,983.98
  5. Step 5: Solve for x
    x = 426,983.98/661.78
  6. Step 6: Final answer
    x = 645.21

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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.