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Finding the Fourth Proportional to 420.85, 631.28 and 128.35

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Solution

The fourth proportional to 420.85, 631.28 and 128.35 is: 192.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.85 : 631.28 = 128.35 : x
  2. Step 2: Convert to fraction form
    420.85/631.28 = 128.35/x
  3. Step 3: Cross multiply
    420.85x = 631.28 × 128.35
  4. Step 4: Simplify right side
    420.85x = 81,024.15
  5. Step 5: Solve for x
    x = 81,024.15/420.85
  6. Step 6: Final answer
    x = 192.53

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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.