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Finding the Fourth Proportional to 642.80, 886.72 and 421.76

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Solution

The fourth proportional to 642.80, 886.72 and 421.76 is: 581.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.80 : 886.72 = 421.76 : x
  2. Step 2: Convert to fraction form
    642.80/886.72 = 421.76/x
  3. Step 3: Cross multiply
    642.80x = 886.72 × 421.76
  4. Step 4: Simplify right side
    642.80x = 373,983.03
  5. Step 5: Solve for x
    x = 373,983.03/642.80
  6. Step 6: Final answer
    x = 581.80

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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.