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Finding the Fourth Proportional to 667.72, 921.21 and 387.80

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Solution

The fourth proportional to 667.72, 921.21 and 387.80 is: 535.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    667.72 : 921.21 = 387.80 : x
  2. Step 2: Convert to fraction form
    667.72/921.21 = 387.80/x
  3. Step 3: Cross multiply
    667.72x = 921.21 × 387.80
  4. Step 4: Simplify right side
    667.72x = 357,245.24
  5. Step 5: Solve for x
    x = 357,245.24/667.72
  6. Step 6: Final answer
    x = 535.02

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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.