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Finding the Fourth Proportional to 642.36, 885.42 and 420.72

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Solution

The fourth proportional to 642.36, 885.42 and 420.72 is: 579.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    642.36 : 885.42 = 420.72 : x
  2. Step 2: Convert to fraction form
    642.36/885.42 = 420.72/x
  3. Step 3: Cross multiply
    642.36x = 885.42 × 420.72
  4. Step 4: Simplify right side
    642.36x = 372,513.90
  5. Step 5: Solve for x
    x = 372,513.90/642.36
  6. Step 6: Final answer
    x = 579.91

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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.