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Finding the Fourth Proportional to 642.78, 887.18 and 421.34

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Solution

The fourth proportional to 642.78, 887.18 and 421.34 is: 581.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.78 : 887.18 = 421.34 : x
  2. Step 2: Convert to fraction form
    642.78/887.18 = 421.34/x
  3. Step 3: Cross multiply
    642.78x = 887.18 × 421.34
  4. Step 4: Simplify right side
    642.78x = 373,804.42
  5. Step 5: Solve for x
    x = 373,804.42/642.78
  6. Step 6: Final answer
    x = 581.54

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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.