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Finding the Fourth Proportional to 642.78, 886.50 and 421.56

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Solution

The fourth proportional to 642.78, 886.50 and 421.56 is: 581.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.78 : 886.50 = 421.56 : x
  2. Step 2: Convert to fraction form
    642.78/886.50 = 421.56/x
  3. Step 3: Cross multiply
    642.78x = 886.50 × 421.56
  4. Step 4: Simplify right side
    642.78x = 373,712.94
  5. Step 5: Solve for x
    x = 373,712.94/642.78
  6. Step 6: Final answer
    x = 581.40

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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.