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Finding the Fourth Proportional to 420.90, 631.17 and 215.25

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Solution

The fourth proportional to 420.90, 631.17 and 215.25 is: 322.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.90 : 631.17 = 215.25 : x
  2. Step 2: Convert to fraction form
    420.90/631.17 = 215.25/x
  3. Step 3: Cross multiply
    420.90x = 631.17 × 215.25
  4. Step 4: Simplify right side
    420.90x = 135,859.34
  5. Step 5: Solve for x
    x = 135,859.34/420.90
  6. Step 6: Final answer
    x = 322.78

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.