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Finding the Fourth Proportional to 420.75, 631.11 and 128.24

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Solution

The fourth proportional to 420.75, 631.11 and 128.24 is: 192.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.75 : 631.11 = 128.24 : x
  2. Step 2: Convert to fraction form
    420.75/631.11 = 128.24/x
  3. Step 3: Cross multiply
    420.75x = 631.11 × 128.24
  4. Step 4: Simplify right side
    420.75x = 80,930.39
  5. Step 5: Solve for x
    x = 80,930.39/420.75
  6. Step 6: Final answer
    x = 192.35

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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.